A sum invested on simple interest  grows to Rs 22500/- and Rs 25500/- is seven and  nine years respectively. What is the rate percentage of the interest ?Question 4Answera.7.5b.9.6c.12.5d.13.5

The formula for simple interest is I = PRT/100, where I is the interest, P is the principal amount, R is the rate of interest, and T is the time in years.

Given that the sum grows to Rs 22500 in 7 years and Rs 25500 in 9 years, we can infer that the interest accrued in the 2 years between 7 and 9 years is Rs 25500 - Rs 22500 = Rs 3000.

We can substitute these values into the simple interest formula to find the rate of interest:

3000 = P * R * 2 / 100

We don't know the principal amount (P) yet, but we can find it by considering that after 7 years, the sum has grown to Rs 22500. This sum includes both the principal amount and the interest accrued in 7 years. If we subtract the interest for 2 years (Rs 3000) from Rs 22500, we get the principal amount:

P = 22500 - 3000 = Rs 19500

Substituting P = 19500 into the equation:

3000 = 19500 * R * 2 / 100

Solving for R, we get:

R = (3000 * 100) / (19500 * 2) = 7.69

So, the rate of interest is approximately 7.69%, which is closest to option (a) 7.5%.