Question

The ages of Pramod and Rohit are 16 years and 18 years respectively. In what ratio must they invest money at 5% p.a. compounded yearly so that both get the same sum on attaining the age of 25 years?

Answer 1

Let Rs.X and Rs.Y be the money invested by Pramod and Rohit respectively such that they will get the same sum on attaining the age of 25 years.
Pramod will attain the age of 25 years  after 25 - 16 = 9 years
Rohit will attain the age of 25 years  after 25 -18 = 7 years

X`( 1 + 5/100 )^9 = y( 1 + 5/100)^7`

⇒ `"X"/"Y" = 1/( 1 + 5/100 )^2`

⇒ `"X"/"Y" = 400/441`

Pramod and Rohit should invest in 400 : 441 ratio respectively such that they will get the same sum on attaining the age of 25 years.