Question

Amar invests some money at compound interest and finds it will amount to Rs.21600 in 2 years and Rs.31104 in 4 years. Find the sum and rate of interest.

Answer 1

Answer:

Sum = Rs 15000

Interest = 20%

Step-by-step explanation:

A = P(1 + r)ⁿ

The amount is Rs 21600 in 2 years

21600 = P(1 + r)²

P = 21600/(1 + r)²

The amount is Rs 31104 in 4 years

31104 = P(1 + r)⁴

P = 31104/(1 + r)⁴

Solve r:

21600/(1 + r)² =  31104/(1 + r)⁴

21600(1 + r)⁴ = 31104(1 + r)²

21600(1 + r)² = 31104

(1 + r)² = 1.44

1 + r = 1.2

r = 0.2

r = 20%

Find the sum:

P = 21600/(1 + r)²

P = 21600/(1 + 0.2)²

P = Rs 15000

Answer: The sum is Rs 15000 and the interest is 20%