a sum of money becomes rs 13380 after 3years and 20070..., Compound Interest, General Mathematics

Question:A sum of money becomes Rs. `13380` after `3`years and Rs. Rs. `20070` after `6` years on compound interest .The sum is :

A `Rs. 8800` 
B `Rs. 8890` 
C `Rs. 8920` 
D `Rs. 9040`

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+ AnswerC

+ ExplanationLet the sum be x. Then,

`x(1 + R/100)^3`

`= 13380  &  x (1 + R/100)^6`

`= 20070`

On diiving, we get `(1 + R/100)^3`

`= 20070/13380`

`= 3/2`

`:. x xx 3/2 = 13380 ⇒ x`

`= (13380 xx 2/3)`

`= 8920`.

Hence, the sum is Rs.`8920`.

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