Question

A certain sum of money amounts to Rs. 1008 in 2 years and to Rs. 1164 in 3 ½ years. Find the sum and rate of interest

Answer 1

As we know,Amount=principal+simple interest
First equation (for 2 years) is 
1008=p+(SI for 2years) -----(1)
second equation (for 3 1/2 years) is
1164=p+(SI for 3 1/2years) -----(2)
subtracting equation (1) and (2) we get
(SI for 3 1/2years)-(SI for 2years)=1164-1008
SI for 1 1/2 year=156
3/2 SI=156
SI for 1year=156*2/3=104
substitute SI value in equation(1),we get
1008=p+(2*SI for 1year)
1008=P+(2*104)
principal=1008-208=800=sum
SI for 2years=P*T*R/100
208=800*2*R/100
Finally,we get R 
R=208*100/(800*2)=13

Answer 2

Your ans. is 10% Maybe it's right or wrong bcz I have done this as a rough work .