Question

At what rate percent per annum wil will a sum of money double itself in eight years.

Answer 1

after eight years the sum becomes amount

let sum p

after eight years the sum becomes double
2p means it becomes amount

simple interest is amount -principal
means 2p -p =p =si


rate of interest formula=si ×100÷principal ×time

=p×100÷p×8=12.5