Question

On a certain sum of money, invested at the rate of 10 percent per annum compounded annually, the interest for the first year plus the interest for the third year is Rs. 2,652. Find the sum.

Answer 1

Let Principal = Rs.100
For 1^st year
P = Rs. 100; R = 10 % and T = 1 year

Interest = Rs.`[100 xx 10 xx 1]/100` = Rs. 10

Amount = Rs. 100 + Rs. 10 = Rs. 110

For 2^nd year

P = Rs. 110; R = 10 % and T = 1 year

Interest = Rs. `[110 xx 10 xx 1]/[100]` = Rs. 11

Amount = Rs. 110 + Rs. 11 = Rs. 121

For 3^rd year

P = Rs. 121; R = 10 % and T = 1 year

Interest = Rs `[121 xx 10 xx 1]/[100]`= Rs. 12.10

Sum of C.I. for 1^st year and 3^rd year = Rs. 10 + Rs. 12.10 = Rs. 22.10

When sum is Rs. 22.10, principal is Rs. 100

When sum is Rs. 2,652, principal = Rs. `[100 xx 2652]/[22.10]`
= Rs. 12,000.