Simple Interest — Extra Practice

Competitive Mathematics · Arithmetic

6 Part16 worked examples114 practice questions

NoteThis is the Extra Practice set: lots of questions. To learn the methods first, read the main chapter of the same topic (the one without “Extra Practice” in its name), then practise here.

Just as you pay rent to use a car, you pay “rent” for using someone’s money — that is interest. The money borrowed is the principal ( $P$ ), the yearly rent rate the rate of interest ( $R %$ ), the period for which it is kept the time ( $T$ ), and the total returned the amount ( $A$ ). In simple interest the interest is charged each year only on the original sum, so it is the same every year.

∑ Formula

S I = \frac{P \times R \times T}{100}, A = P + S I = P (1 + \frac{R T}{100})

The two core formulas

$P$: principal
$R$: rate per annum (%)
$T$: time (in years)
$A$: amount

The formula and its four forms

Finding any one of

S I

P

R

T

Given three of the four quantities, finding the fourth.

Interest, principal, rate, time

Turning the formula around

The formula for each variable and solved examples.

To find	Formula
SI	$\frac{P R T}{100}$
P	$\frac{S I \times 100}{R T} या \frac{A \times 100}{100 + R T}$
R	$\frac{S I \times 100}{P T}$
T	$\frac{S I \times 100}{P R}$

Example 1 · Basic

Find the simple interest and the amount on ₹7,500 at 8% per annum for 3 years.

Solution, step by step

1 $S I = \frac{7500 \times 8 \times 3}{100} = 1800$ .
2Amount $= 7500 + 1800 = 9300$

Answer ₹1,800 and ₹9,300

Example 2 · Standard

A sum amounts to ₹7,200 in 4 years at 5% simple interest per annum. What was the sum?

Solution, step by step

1 $A = P (1 + \frac{5 \times 4}{100}) = 1.2 P$ .
2 $P = \frac{7200}{1.2} = 6000$

Answer ₹6,000

Example 3 · Standard

₹4,000 earned ₹960 simple interest in 3 years. What is the rate per annum?

Solution, step by step

1 $R = \frac{960 \times 100}{4000 \times 3}$ .
2 $= 8%$

Answer 8%

Example 4 · Advanced

Part of ₹15,000 is lent at 6% and the rest at 8% per annum, and the total interest in 1 year is ₹1,060. How much is at 8%?

Solution, step by step

1If all were at 6% the interest would be $900$ . The gap is $1060 - 900 = 160$ .
2Each rupee at 8% adds 2% extra ⟹ the 8% part $= \frac{160}{0.02} = 8000$ .

Answer ₹8,000

BasicTry it yourself first

What is the simple interest on ₹3,000 at 6% per annum for 4 years?

BasicTry it yourself first

What is the simple interest on ₹5,600 at 5% per annum for 2 years?

StandardTry it yourself first

What is the simple interest on ₹12,500 at 7.5% per annum for 3 years?

BasicTry it yourself first

₹2,000 is lent at 10% simple interest per annum for 3 years. What is the amount?

StandardTry it yourself first

₹8,400 is lent at 6.5% simple interest per annum for 5 years. What is the amount?

BasicTry it yourself first

A sum at 10% simple interest per annum amounts to ₹5,600 in 4 years. What was the principal?

StandardTry it yourself first

A sum at 6% simple interest per annum amounts to ₹13,000 in 5 years. What was the principal?

AdvancedTry it yourself first

A sum at 7.5% simple interest per annum amounts to ₹15,600 in 4 years. What was the principal?

BasicTry it yourself first

₹2,000 earns ₹400 simple interest in 4 years. What is the rate per annum?

StandardTry it yourself first

₹7,500 earns ₹1,350 simple interest in 3 years. What is the rate per annum?

AdvancedTry it yourself first

₹16,000 earns ₹3,520 simple interest in 2.5 years. What is the rate per annum?

BasicTry it yourself first

In how many years will ₹4,000 become ₹5,200 at 10% simple interest per annum?

StandardTry it yourself first

In how many years will ₹6,500 become ₹8,255 at 7.5% simple interest per annum?

AdvancedTry it yourself first

In how many years will ₹9,000 become ₹11,340 at 4% simple interest per annum?

Units of time

Days · months · half-years · quarters

If the rate is yearly, convert the time to years; if it is half-yearly or quarterly, convert it to a yearly rate.

Time	In years
1 month	$\frac{1}{12}$
3 months	$\frac{1}{4}$
9 months	$\frac{3}{4}$
73 days	$\frac{73}{365} = \frac{1}{5}$
146 days	$\frac{2}{5}$

RememberA half-yearly rate means that much interest every 6 months; the yearly rate is double. For a quarterly rate it is four times. In simple interest there is no interest on interest, so simply converting to a yearly rate works.

When counting days, the day the money is deposited is not counted but the day it is withdrawn is. Usually 1 year = 365 days.

Example 5 · Standard

What is the simple interest on ₹14,600 at 10% per annum for 146 days?

Solution, step by step

1 $T = \frac{146}{365} = \frac{2}{5}$ year.
2 $S I = 14600 \times \frac{10}{100} \times \frac{2}{5} = 584$

Answer ₹584

Example 6 · Standard

Find the simple interest on ₹6,000 at 3% half-yearly for 2 years.

Solution, step by step

1Annual rate $= 3 \times 2 = 6%$ .
2 $S I = \frac{6000 \times 6 \times 2}{100} = 720$

Answer ₹720

Example 7 · Standard

In what time will ₹8,000 become ₹9,080 at 4.5% simple interest per annum?

Solution, step by step

1Interest $= 9080 - 8000 = 1080$ .
2 $T = \frac{1080 \times 100}{8000 \times 4.5} = 3$ years

Answer 3 years

BasicTry it yourself first

What is the simple interest on ₹10,000 at 6% per annum for 73 days? (1 year = 365 days)

StandardTry it yourself first

What is the simple interest on ₹18,250 at 6% per annum for 146 days? (1 year = 365 days)

AdvancedTry it yourself first

What is the simple interest on ₹21,900 at 5% per annum for 219 days? (1 year = 365 days)

BasicTry it yourself first

What is the total simple interest on ₹5,000 at 2% half-yearly for 3 years?

StandardTry it yourself first

What is the total simple interest on ₹8,000 at 1.5% quarterly for 2 years?

StandardTry it yourself first

What is the total simple interest on ₹12,000 at 4% half-yearly for 2.5 years?

AdvancedTry it yourself first

What is the total simple interest on ₹15,000 at 2.5% quarterly for 3 years?

StandardTry it yourself first

A man borrows ₹20,000 at 6% per annum and lends the same sum at 8.5%. What is his gain in 3 years?

AdvancedTry it yourself first

A man borrows ₹36,000 at 7.25% per annum and lends the same sum at 9%. What is his gain in 4 years?

$n$ times, two sums and two amounts

Interest from multiples of the principal

How many times the sum grows, how much interest and how long; and finding the principal from two amounts.

A sum becoming $n$ times

Interest

= (n - 1) \times

principal

Rate-time relations when a sum doubles, triples, and so on.

∑ Formula

R = \frac{( n - 1 ) \times 100}{T}, T = \frac{( n - 1 ) \times 100}{R}

A sum becomes

n

times in

T

years

Idea: becoming $n$ times means amount $= n P$ , i.e. interest $= (n - 1) P$ . When the interest multiple grows, time grows in the same ratio: if $T_{1}$ years make it $n_{1}$ times, then it takes $T_{2} = T_{1} \times \frac{n _{2} - 1}{n _{1} - 1}$ years to make it $n_{2}$ times.

Example 8 · Standard

At simple interest a sum becomes 3 times in 12 years. Find the rate and how long it takes to become 7 times.

Solution, step by step

1Rate $= \frac{( 3 - 1 ) \times 100}{12} = 16 \frac{2}{3} %$ .
2For 7 times: $T = 12 \times \frac{6}{2} = 36$ years.

Answer $16 \frac{2}{3} %$ and 36 years

Example 9 · Standard

A sum doubles in 6 years. In how many years will it become 5 times?

Solution, step by step

1Interest multiples: 1 → 4.
2Time $= 6 \times \frac{5 - 1}{2 - 1} = 24$ years

Answer 24 years

BasicTry it yourself first

A sum becomes 2 times itself in 8 years at simple interest. What is the rate per annum?

StandardTry it yourself first

A sum becomes 3 times itself in 16 years at simple interest. What is the rate per annum?

StandardTry it yourself first

A sum becomes 5 times itself in 20 years at simple interest. What is the rate per annum?

AdvancedTry it yourself first

A sum becomes 4 times itself in 30 years at simple interest. What is the rate per annum?

BasicTry it yourself first

A sum becomes 2 times in 5 years. In how many years will it become 4 times at the same rate?

StandardTry it yourself first

A sum becomes 3 times in 10 years. In how many years will it become 6 times at the same rate?

AdvancedTry it yourself first

A sum becomes 4 times in 12 years. In how many years will it become 11 times at the same rate?

Two sums, two amounts

Take the difference

The gain from borrowing and lending, the difference of two rates, a split sum and two amounts.

Two amounts ( $A_{1}$ after $T_{1}$ years, $A_{2}$ after $T_{2}$ years): interest per year $= \frac{A _{2} - A _{1}}{T _{2} - T _{1}}$ ; principal $= A_{1} - T_{1} \times$ (interest per year).
Difference of two rates: difference in interest $= \frac{P ( R _{2} - R _{1} ) T}{100}$ .
A sum in two parts: one part $x$ , the other $S - x$ ; form the total-interest equation, or assume the whole sum at one rate and find the gap.
Equal interest gives $P_{1} R_{1} T_{1} = P_{2} R_{2} T_{2}$ .

Example 10 · Standard

A sum amounts to ₹6,500 in 3 years and ₹7,500 in 5 years at simple interest. Find the principal and the rate.

Solution, step by step

1Interest for 2 years $= 1000$ ⟹ for 1 year $= 500$ .
2Principal $= 6500 - 3 \times 500 = 5000$ ; rate $= \frac{500}{5000} \times 100 = 10%$ .

Answer ₹5,000 and 10%

Example 11 · Advanced

₹12,000 is invested partly at 6% and the rest at 9% simple interest per annum for 2 years, giving ₹1,800 in all. How much was at 6%?

Solution, step by step

1If all were at 6% the interest would be $\frac{12000 \times 6 \times 2}{100} = 1440$ . The gap is $360$ .
2Each rupee at 9% adds $3% \times 2 = 6%$ ⟹ the 9% part $= \frac{360}{0.06} = 6000$ ; so the 6% part is also ₹6,000.

Answer ₹6,000

Example 12 · Standard

The difference between the simple interest on a sum for 3 years at 5% and at 8% per annum is ₹630. Find the sum.

Solution, step by step

1Difference in rates $= 3%$ , time 3 years ⟹ difference in interest $= 9%$ of $P$ .
2 $P = \frac{630 \times 100}{9} = 7000$

Answer ₹7,000

Example 13 · Standard

Ramesh borrows ₹40,000 at 7% and lends it at 9.5%. What is his gain in 3 years?

Solution, step by step

1Yearly gain $= 40000 \times \frac{9.5 - 7}{100} = 1000$ .
2In 3 years $= 3000$

Answer ₹3,000

StandardTry it yourself first

A man borrows ₹25,000 at 6% per annum and lends the same sum at 9.5%. What is his gain in 2 years?

BasicTry it yourself first

A sum amounts to ₹4,800 in 2 years and ₹5,600 in 4 years at simple interest. What is the principal?

StandardTry it yourself first

A sum amounts to ₹9,300 in 3 years and ₹10,500 in 5 years at simple interest. What is the principal?

AdvancedTry it yourself first

A sum amounts to ₹15,600 in 4 years and ₹17,400 in 6 years at simple interest. What is the principal?

StandardTry it yourself first

The difference between the simple interest on a sum for 3 years at 6% and at 8.5% per annum is ₹600. What is the sum?

AdvancedTry it yourself first

The difference between the simple interest on a sum for 4 years at 5.5% and at 9% per annum is ₹2,100. What is the sum?

StandardTry it yourself first

A sum of ₹10,000 is partly invested at 6% and the rest at 9% simple interest per annum for 2 years, earning ₹1,440 in all. How much is invested at 6%?

AdvancedTry it yourself first

A sum of ₹15,000 is partly invested at 5% and the rest at 8% simple interest per annum for 3 years, earning ₹2,790 in all. How much is invested at 5%?

StandardTry it yourself first

On what sum will the simple interest in 4 years at 6% equal the interest on ₹6,000 at 8% in 3 years?

AdvancedTry it yourself first

On what sum will the simple interest in 3 years at 5% equal the interest on ₹7,500 at 6% in 4 years?

Payment by instalments

Interest on the time each instalment stays unpaid

Comparing a cash price with an instalment scheme; the value of equal instalments.

Equal monthly instalments

No interest on the last instalment

Each instalment carries interest for the months it stays unpaid.

In $n$ equal monthly instalments the last instalment is paid on the day the debt ends — no interest on it. The one before was paid a month early, so the lender’s money earned an extra month — interest of 1 month on it; likewise the first instalment carries $(n - 1)$ months of interest. Hence the balance $= n x + x \times \frac{R}{1200} \times \frac{n ( n - 1 )}{2}$ , with $x$ each instalment.

Example 14 · Standard

A TV costs ₹15,300 cash, or ₹3,000 down and the rest in 4 equal monthly instalments. The rate is 20% per annum (simple). Find each instalment.

Solution, step by step

1Balance $= 12300$ . Formula: $4 x + x \times \frac{20}{1200} \times 6 = 12300$ (the instalments are 3, 2, 1, 0 months late: 6 months in all).
2 $4.1 x = 12300$ ⟹ $x = 3000$

Answer ₹3,000

Example 15 · Standard

An article of ₹7,600 is sold for ₹2,500 down and 5 equal monthly instalments at 12% per annum (simple). Find each instalment.

Solution, step by step

1Balance $= 5100$ . Formula: $5 x + x \times \frac{12}{1200} \times 10 = 5100$ .
2 $5.1 x = 5100$ ⟹ $x = 1000$

Answer ₹1,000

BasicTry it yourself first

An article costs ₹7,600 cash, or ₹2,500 down and the rest in 5 equal monthly instalments. The company charges 12% simple interest per annum. What is each instalment?

StandardTry it yourself first

An article costs ₹20,000 cash, or ₹3,640 down and the rest in 4 equal monthly instalments. The company charges 18% simple interest per annum. What is each instalment?

StandardTry it yourself first

An article costs ₹18,500 cash, or ₹3,000 down and the rest in 6 equal monthly instalments. The company charges 16% simple interest per annum. What is each instalment?

AdvancedTry it yourself first

An article costs ₹18,000 cash, or ₹2,700 down and the rest in 3 equal monthly instalments. The company charges 24% simple interest per annum. What is each instalment?

AdvancedTry it yourself first

An article costs ₹20,000 cash, or ₹3,300 down and the rest in 8 equal monthly instalments. The company charges 15% simple interest per annum. What is each instalment?

AdvancedTry it yourself first

An article costs ₹25,000 cash, or ₹4,100 down and the rest in 10 equal monthly instalments. The company charges 12% simple interest per annum. What is each instalment?

Traps and fast tricks

Slips · tricks

Where marks are lost in simple interest.

The commonest mistakes

Six traps

The slips that cost marks.

Trap 1Not converting time to years. 9 months

= \frac{3}{4}

year, not 9.

Trap 2Treating the amount as the principal. “Became ₹5,000” means interest = 5,000 − principal.

Trap 3Using $n$ as the interest multiple when a sum becomes $n$ times. The interest is

(n - 1)

times.

Trap 4Reading a half-yearly rate as yearly. 3% half-yearly = 6% yearly.

Trap 5Charging every instalment the same interest. The first carries the most months, the last none.

Trap 6Mixing 360 and 365 days. Use what the question says; if nothing is said, 365.

Fast tricks

Multipliers and ratios

Tricks that shorten the work.

Amount multiplier: $1 + \frac{RT}{100}$ . 5%, 4 years ⟹ ×1.2; 8%, 5 years ⟹ ×1.4.
If two of $P$ , $R$ , $T$ change, use ratios: interest $\propto P \times R \times T$ .
For a sum to double: $R \times T = 100$ .
For $n$ times: $R T = (n - 1) \times 100$ .
Equal interest at different rates: $P_{1} R_{1} T_{1} = P_{2} R_{2} T_{2}$ .

Example 16 · Standard

At some rate a sum triples in 8 years. In how many years will it become 5 times at the same rate?

Solution, step by step

1Interest multiples 2 → 4 (double).
2Time also doubles: 16 years

Answer 16 years

The practice ladder

Basic → standard → advanced

New questions of every type, in three levels.

Level 1 — Basic

Direct rules

One-rule questions.

BasicTry it yourself first

What is the simple interest on ₹4,500 at 8% per annum for 2 years?

BasicTry it yourself first

What is the simple interest on ₹10,000 at 5% per annum for 3 years?

BasicTry it yourself first

₹6,000 is lent at 5% simple interest per annum for 4 years. What is the amount?

BasicTry it yourself first

₹3,500 is lent at 10% simple interest per annum for 2 years. What is the amount?

BasicTry it yourself first

A sum at 10% simple interest per annum amounts to ₹6,500 in 3 years. What was the principal?

BasicTry it yourself first

A sum at 5% simple interest per annum amounts to ₹5,400 in 4 years. What was the principal?

BasicTry it yourself first

₹5,000 earns ₹1,500 simple interest in 3 years. What is the rate per annum?

BasicTry it yourself first

₹8,000 earns ₹960 simple interest in 2 years. What is the rate per annum?

BasicTry it yourself first

In how many years will ₹5,000 become ₹6,500 at 6% simple interest per annum?

BasicTry it yourself first

In how many years will ₹2,500 become ₹3,000 at 4% simple interest per annum?

BasicTry it yourself first

What is the simple interest on ₹36,500 at 5% per annum for 73 days? (1 year = 365 days)

BasicTry it yourself first

What is the total simple interest on ₹4,000 at 3% half-yearly for 2 years?

BasicTry it yourself first

A sum becomes 3 times itself in 10 years at simple interest. What is the rate per annum?

BasicTry it yourself first

A sum becomes 2 times in 4 years. In how many years will it become 3 times at the same rate?

BasicTry it yourself first

A man borrows ₹10,000 at 5% per annum and lends the same sum at 7%. What is his gain in 2 years?

BasicTry it yourself first

A sum amounts to ₹5,600 in 2 years and ₹5,900 in 3 years at simple interest. What is the principal?

BasicTry it yourself first

The difference between the simple interest on a sum for 2 years at 4% and at 6% per annum is ₹200. What is the sum?

BasicTry it yourself first

A sum of ₹4,000 is partly invested at 5% and the rest at 10% simple interest per annum for 1 year, earning ₹300 in all. How much is invested at 5%?

BasicTry it yourself first

On what sum will the simple interest in 5 years at 4% equal the interest on ₹4,000 at 5% in 2 years?

BasicTry it yourself first

An article costs ₹7,600 cash, or ₹2,500 down and the rest in 5 equal monthly instalments. The company charges 12% simple interest per annum. What is each instalment?

Level 2 — Standard

Two ideas combined

Exam-level questions.

StandardTry it yourself first

What is the simple interest on ₹16,800 at 6.5% per annum for 4 years?

StandardTry it yourself first

What is the simple interest on ₹27,500 at 8% per annum for 2.5 years?

StandardTry it yourself first

₹14,400 is lent at 7.5% simple interest per annum for 4 years. What is the amount?

StandardTry it yourself first

A sum at 6% simple interest per annum amounts to ₹9,440 in 3 years. What was the principal?

StandardTry it yourself first

A sum at 7% simple interest per annum amounts to ₹11,520 in 4 years. What was the principal?

StandardTry it yourself first

₹9,600 earns ₹2,304 simple interest in 4 years. What is the rate per annum?

StandardTry it yourself first

₹12,500 earns ₹1,875 simple interest in 2 years. What is the rate per annum?

StandardTry it yourself first

In how many years will ₹8,000 become ₹10,400 at 6.5% simple interest per annum?

StandardTry it yourself first

In how many years will ₹12,000 become ₹15,600 at 5% simple interest per annum?

StandardTry it yourself first

What is the simple interest on ₹29,200 at 5% per annum for 146 days? (1 year = 365 days)

StandardTry it yourself first

What is the total simple interest on ₹9,000 at 2.5% quarterly for 3 years?

StandardTry it yourself first

What is the total simple interest on ₹7,500 at 3.5% half-yearly for 2 years?

StandardTry it yourself first

A sum becomes 4 times itself in 12 years at simple interest. What is the rate per annum?

StandardTry it yourself first

A sum becomes 6 times itself in 25 years at simple interest. What is the rate per annum?

StandardTry it yourself first

A sum becomes 2 times in 9 years. In how many years will it become 5 times at the same rate?

StandardTry it yourself first

A sum becomes 3 times in 8 years. In how many years will it become 7 times at the same rate?

StandardTry it yourself first

A man borrows ₹45,000 at 6.5% per annum and lends the same sum at 8%. What is his gain in 3 years?

StandardTry it yourself first

A sum amounts to ₹10,350 in 3 years and ₹12,150 in 7 years at simple interest. What is the principal?

StandardTry it yourself first

A sum amounts to ₹7,360 in 2 years and ₹9,280 in 6 years at simple interest. What is the principal?

StandardTry it yourself first

The difference between the simple interest on a sum for 2 years at 5% and at 7.5% per annum is ₹600. What is the sum?

StandardTry it yourself first

A sum of ₹12,000 is partly invested at 6% and the rest at 8% simple interest per annum for 3 years, earning ₹2,460 in all. How much is invested at 6%?

StandardTry it yourself first

A sum of ₹12,000 is partly invested at 4% and the rest at 7% simple interest per annum for 2 years, earning ₹1,200 in all. How much is invested at 4%?

StandardTry it yourself first

On what sum will the simple interest in 3 years at 6% equal the interest on ₹9,000 at 7% in 2 years?

StandardTry it yourself first

An article costs ₹20,000 cash, or ₹3,640 down and the rest in 4 equal monthly instalments. The company charges 18% simple interest per annum. What is each instalment?

StandardTry it yourself first

An article costs ₹18,500 cash, or ₹3,000 down and the rest in 6 equal monthly instalments. The company charges 16% simple interest per annum. What is each instalment?

Level 3 — Advanced

Many steps and clever thinking

Questions at the hard end of competitive exams.

AdvancedTry it yourself first

What is the simple interest on ₹38,500 at 7.25% per annum for 3.5 years?

AdvancedTry it yourself first

A sum at 7.5% simple interest per annum amounts to ₹19,250 in 5 years. What was the principal?

AdvancedTry it yourself first

A sum at 6.5% simple interest per annum amounts to ₹27,800 in 6 years. What was the principal?

AdvancedTry it yourself first

₹28,000 earns ₹8,820 simple interest in 3.5 years. What is the rate per annum?

AdvancedTry it yourself first

In how many years will ₹24,000 become ₹30,960 at 4.5% simple interest per annum?

AdvancedTry it yourself first

What is the simple interest on ₹43,800 at 7.5% per annum for 219 days? (1 year = 365 days)

AdvancedTry it yourself first

What is the total simple interest on ₹24,000 at 2.25% quarterly for 4 years?

AdvancedTry it yourself first

A sum becomes 5 times itself in 22 years at simple interest. What is the rate per annum?

AdvancedTry it yourself first

A sum becomes 8 times itself in 28 years at simple interest. What is the rate per annum?

AdvancedTry it yourself first

A sum becomes 3 times in 9 years. In how many years will it become 8 times at the same rate?

AdvancedTry it yourself first

A sum becomes 5 times in 20 years. In how many years will it become 9 times at the same rate?

AdvancedTry it yourself first

A man borrows ₹64,000 at 6.75% per annum and lends the same sum at 8.25%. What is his gain in 2.5 years?

AdvancedTry it yourself first

A sum amounts to ₹17,925 in 3 years and ₹22,800 in 8 years at simple interest. What is the principal?

AdvancedTry it yourself first

A sum amounts to ₹24,780 in 2 years and ₹30,450 in 5 years at simple interest. What is the principal?

AdvancedTry it yourself first

The difference between the simple interest on a sum for 3 years at 6.25% and at 9.75% per annum is ₹2,940. What is the sum?

AdvancedTry it yourself first

The difference between the simple interest on a sum for 2.5 years at 4.5% and at 7.5% per annum is ₹2,700. What is the sum?

AdvancedTry it yourself first

A sum of ₹20,000 is partly invested at 7% and the rest at 11% simple interest per annum for 4 years, earning ₹6,880 in all. How much is invested at 7%?

AdvancedTry it yourself first

A sum of ₹24,000 is partly invested at 5.5% and the rest at 8.5% simple interest per annum for 3 years, earning ₹4,770 in all. How much is invested at 5.5%?

AdvancedTry it yourself first

On what sum will the simple interest in 6 years at 5% equal the interest on ₹12,500 at 6.5% in 3 years?

AdvancedTry it yourself first

On what sum will the simple interest in 5 years at 6% equal the interest on ₹16,000 at 7.5% in 2 years?

AdvancedTry it yourself first

An article costs ₹18,000 cash, or ₹2,700 down and the rest in 3 equal monthly instalments. The company charges 24% simple interest per annum. What is each instalment?

AdvancedTry it yourself first

An article costs ₹20,000 cash, or ₹3,300 down and the rest in 8 equal monthly instalments. The company charges 15% simple interest per annum. What is each instalment?

AdvancedTry it yourself first

An article costs ₹25,000 cash, or ₹4,100 down and the rest in 10 equal monthly instalments. The company charges 12% simple interest per annum. What is each instalment?

Revision — formula cards

Flip each card and test yourself

Read the front, think, then flip.