Question

8. A certain sum given on simple interest became
double in 20 yr. In how many years will it be four
times?
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Answer 1

Answer:

Let the money be = x

Amount = 2x

Simple interest = x

S.I. = PRT/100

=> x = x × R × 20/100

=> R = 5 %

When Amount = 4x

Simple interest = 3x

S.I. = PRT/100

=> 3x = x × T × 5/100

=> T = 60 years

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Answer 2

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Let the sum of money be X

SI=Amount-Principal

In this case, Simple Interest is = X

SI=P×R×T/100

X=XR×20/100

100x/20x=R

5%=R

Amount = 4x,

In this case SI=4x-x=3x

SI=P×R×T/100

3x=X×5×T/100

3x/X=T×1/20

3×20=T

60=T

So it will take 60 years to make the sum of money tripled.

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