Question

A sum of money amounts to 10.400 in 6 years and

11.200 in 8 years. Find the sum and rate of interest
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Answer 1

Answer:

Make it simple by using conventional method

In case of compound interest:-

A = P*(1+R/100)^T

Let the initial principal is Rs.X which amounts to Rs.10400 in 6 years

10400 = X*(1+R/100)^6

(1+R/100)^6 = 10400/X …….(1)

After 6 year new principal will be 10400 which amounts to Rs.11500 in another 2 years

11500 = 10400*(1+R/100)^2

(1+R/100)^2 = 11500/10400 or 115/104

(1+R/100)^2 = 115/104

By taking cube both the sides

{(1+R/100)^2}^3 = (115/104)^3

(1+R/100)^6 = (115/104)^3

Putting this value of (1+R/100)^6 in equation (1)

(115/104)^3 = 10400/X

X = (10400*104*104*104)/(115*115*115)

X = 7692 approx

By putting this value in any equation we can find R