Question

If a certain sum of money doubles itself in 7
years 8 months at simple interest, then what will
be the yearly rate of interest (in %)?​

Answer 1

Answer:-

Let the sum (P) be "x".

Given:

Time period = 7 years 8 months

1 year = 12 months

→ 7 years 8 months = 7 * 12 + 8

→ Time Period = 92 months

→ Time Period (T) = 92/12 = 23/3 years.

And,

The sum doubles itself in 23/3 years.

→ Simple Interest = 2*x = 2x

We know that,

Simple Interest = PTR/100

[ R is the rate of interest ]

→ 2x = (x) * (23/3) * R/100

→ 2x = (23x/ 3) * 1/100 * R

→ R = (2x) * (3/23x) * 100

→ R = 26.08 % = 26 % (Approx.)

Therefore, the rate of interest will be 26 % .