A certain sum at simple interest amounts to Rs.1350 in 5 years

A certain sum at simple interest amounts to Rs.1350 in 5 years and to Rs.1620 in 8 years. What is the sum?

  1. Rs.900
  2. Rs.800
  3. Rs.700
  4. Rs.1000

Answer

SI = PRT/100 and Amount, A = P + SI

SI = A - P

A - P = PRT/100

In 5 years, 1350 - P = P*R*5/100

In 8 years, 1620 - P = P*R*8/100

Divide both equations,

(1350 - P)/(1620 - P) = 5/8

10800 - 8P = 8100 - 5P

P = 900

The correct option is A.