Question

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 1

C.I = A - P 

4240 = `"P"( 1 + "r"_1/100)( 1 + "r"_2/100)- "P"`

4240 = P `[( 1 + 10/100 )( 1 + 15/100)-1]`

4240 = P `[11/10xx115/100-1]`

4240 = P `[1265/1000-1]`

4240 = P `[(1265-1000)/1000]`

4240 = P `[265/1000]`

`(4240xx1000)/265` = P 

16000 = P

The sum is Rs. 16,000.