Question

No. of years a sum 4 times itself at 12% pa at simple interest: (a) 20 (b) 21 (c) 25 (d) 30

Answer 1

Let Sum=₹x

At 12% Annum.

It become 4 times.

Amount=4x

SI=Amount-Sum

=4x-x

=3x

SI=₹3x

Sum=₹x

Rate=12%

Time=?

We know.

$\boxed{\mathtt{SI=\frac{Sum\times\:Rate\:\times\:Time}{100}}}$

$\boxed{\mathtt{3x=\frac{x\times\:12\:\times\:Time}{100}}}$

$\boxed{\mathtt{\frac{3x\times100}{12x}=Time}}$

$\boxed{\mathtt{\frac{300x}{12x}=Time}}$

$\boxed{\mathtt{25\:years=Time}}$

Hence Option c is correct

$\boxed{\mathtt{\huge{Time=25\:years}}}$