Question

A certain sum amounts to ₹2200 in 2 years to ₹2800 in 4 years at simple interest. Find the sum and the rate per cent per annum.

Answer 1

Let the Principal be P
P R T/100 = simple interest.
So as per conditions after 4 years:
P+(P*R*4/100)=2800

As per 2nd condition
P+(P*R*2/100)=2200

Subtract 2equation from 1

2P*R/100=600
P*R=30000 ____(3)

Put the value of P*R in equation 1

P+(30000*4/100)=2800 =>P=1600
R=18.75% (using 3)