Question

At what rate percent per annum will a sum of rs 640 be compounded

Answer 1

774.40=640(1+r/100)²
774.40/640=(1+r/100)²
(1.1)²=(1+r/100)²
1.1=1+r/100
r/100=1.1-1
r/100=0.1
r=0.1*100
r=10%pa