# Compound Interest Using Formula Concise ICSE Class-9th

## Chapter/ Lesson / Exercise -3 Compound Interest (Using Formula) Selina Mathematics Solutions

**Compound Interest Using Formula** Concise ICSE Class-9th Mathematics Selina solutions Chapter-3 . We provide step by step Solutions of Exercise / lesson-3 **Compound Interest (Using Formula) ** for ICSE Class-9 Concise Selina Mathematics by RK Bansal.

Our Solutions contain all type Questions with Exe-3 A, Exe-3 B, Exe-3 C, Exe-3 D and Exe-3 E to develop skill and confidence. Visit official Website **CISCE** for detail information about ICSE Board Class-9 Mathematics .

**Compound Interest Using Formula** Concise ICSE Class-9th Mathematics Selina solutions Chapter-3

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### Exercise – 3(A) **Compound Interest (Using Formula**) Concise Selina Mathematics ICSE Class-9th

#### Question 1

Find the amount and the compound interest on Rs. 12,000 in 3 years at 5% compounded annually.

**Answer**

Given : P= Rs. 12,000; n = 3 years and r = 5%

= Rs. 13,891.50

C.I. = Rs. 13,891.50 – Rs. 12,000 = Rs. 1,891.50.

#### Question 2

Calculate the amount of Rs. 15,000 is lent at compound interest for 2 years and the rates for the successive years are 8% and 10% respectively.

**Answer**

**Given :** P = Rs. 15,000; n = 2 years; r_{1} = 8 % and r_{2} = 10%

= Rs. 17,820.

#### Question 3

**Answer **

Given : P = Rs. 6,000; n = 3 years; r_{1 }= 5%; r_{2 }= 8% and r_{3} = 10%

= Rs. 7,484.40

∴ C.I. = Rs. 7,484.40 – Rs. 6,000 = Rs. 1,484.40.

#### Question 4

What sum of money will amount to Rs. 5,445 in 2 years at 10% per annum compound interest ?

**Answer **

Given : P= Rs. 5,445 ; n = 2 years and r = 10%

⇒ Rs. 4,500

#### Question 5

On what sum of money will the compound interest for 2 years at 5% per annum amount to Rs. 768.75?

**Answer **

**Given :** C.I.= Rs. 768.75; n= 2 years and r = 5%

#### Question 6

Find the sum on which the compound interest for 3 years at 10% per annum amounts to Rs. 1,655.

**Answer **

**Given :** C.I. = Rs. 1,655; n = 3 years and r = 10%

#### Question 7

What principal will amount to Rs. 9,856 in two years, if the rates of interest for successive years are 10% and 12% respectively ?

**Answer **

**Given :** A = Rs. 9,856 ; n = 2 years ; r_{1} = 10 % and r_{2} = 12%

Question 8

On a certain sum, the compound interest in 2 years amounts to Rs. 4,240. If the rate of interest for the successive years is 10% and 15% respectively, find the sum.

**Answer **

‘

⇒ ( P + 4240 ) = P(1.265)

⇒ P = Rs. 16000

The sum is Rs.16,000.

#### Question 9

At what per cent per annum will Rs.6,000 amount to Rs.6,615 in 2 years when interest is compounded annually?

**Answer **

At 5% per annum the sum of Rs. 6,000 amounts to Rs. 6,615 in 2 years when the interest is compounded annually.

#### Question 10

At what rate per cent compound interest, does a sum of money become 1.44 times of itself in 2 years ?

**Answer **

Let Principal = Rs. y

Then Amount= Rs 1.44y

n= 2 years

On solving, we get

r = 20 %

#### Question 11

At what rate per cent will a sum of Rs. 4,000 yield Rs.1,324 as compound interest in 3 years ?

**Answer **

Given : P = Rs. 4,000, C.I. = Rs. 1,324 and n = 3 years

Now, A = P + I

⇒ A = Rs. ( 4,000 + 1,324 ) = Rs. 5,324

Thus, the rate of interest is 10%.

#### Question 12

(i) the rate of interest per annum.

(ii) the amount at the end of the third year.

**Answer **

**Given:** P = Rs. 5,000; A = Rs. 6,272 and n = 2 years.

= Rs. 7,024.64

#### Question 13

In how many years will Rs. 7,000 amount to Rs. 9,317 at 10% per annum compound interest ?

**Answer **

**Given :** P = Rs. 7,000; A = Rs. 9,317 and r = 10%.

On comparing,

n = 3 years

#### Question 14

Find the time, in years, in which Rs. 4,000 will produce Rs. 630.50 as compound interest at 5% compounded annually.

**Answer **

Given : P= Rs. 4,000; C.I.= Rs. 630.50 and r = 5%

On comparing,

n = 3 years

#### Question 15

Divide Rs. 28,730 between A and B so that when their shares are lent out at 10% compound interest compounded per year, the amount that A receives in 3 years is the same as what B receives in 5 years.

**Answer **

Let share of A = Rs. y

share of B = Rs (28,730 – y)

rate of interest= 10%

According to question,

Amount of A in 3 years= Amount of B in 5 years

Therefore share of A = Rs. 15,730

Share of B = Rs. 28,730 – Rs.15,730 = Rs. 13,000

#### Question 16

(i) What is the share of each out of Rs44,200 ?

**Answer **

**(i)** Let share of John = Rs y

share of Smith = Rs (44,200 – y)

rate of interest= 10%

According to question,

Amount of John in 4 years = Amount of Smith in 2 years

= Rs. 29,282

#### Question 17

The simple interest on a certain sum of money and at 10% per annum is Rs. 6,000 in 2 years, Find:

- the sum.
- the amount due to the end of 3 years and at the same rate of interest compounded annually.
- the compound interest earned in 3 years.

**Answer **

(i) I = Rs. 6,000, T = 2 years and R = 10%

= Rs. 39,930

(iii) C.I. earned in 3 years = A – P = Rs. (39,930 – 30,000) = Rs. 930.