Question

a certain sum doubles in 3 years under simple interest. in how many years will the sum become 5 times itself

Answer 1

Let the sum be x
then,amount=2x
si= a-p
= 2x-x
=x
r=( si×100)/p×t
r=(x×100)/x×3
r=100/3
a/q
r=100/3
a=5x
si=4x
t= (si×100)/p×r
(4x×100)/x×100/3
= (4x×100×3)/x×100
= 12 years ans.
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