Question

in what timewill a sum of money double itself at 15% per annum ?

Answer 1

let the principal be p

thus amount=2p

S.I=p

R%=15%

time=100*S.I/P*R

=100*p/p*15

=20/3 years

Answer 2

Let the principal be 'x'
and time be 't'
SI = PRT/100
x = (x * 15 * t) / 100
100x = 15xt
100 = 15t
t = 100/15
= 6 2/3 years
= 6 years 8 months