Question

in what time will a sum of rs3,750 at 20% per annum compounded annually amount to rs 6,480?

Answer 1

let the time be n and here compounded annually
now formula is amount= principal (1+r/100)^n
or. 6480=3750 (1+20/100)^n
or, 6480/3750 = (120/100)^n=(6/5)^n
or, 648/375= (6/5)^n
or, (6*6*6*3)/(5*5*5*3)= (6/5)^n
so (6*6*6)/(5*5*5)=(6/5)^n
or,6^3/5^3=(6/5)^n
or, (6/5)^3=(6/5)^n
implies n= 3 yrs