# What will be the Annual Interest Rate? If

At what rate of annual simple interest, certain sum will amount to four times in 15 year?

- 15%
- 17.5%
- 20%
- 25%

**Answer: (3) 20 %**

**Explanation:-**

Let the rate be R % & principal is P.

Given –

Time = 15 years, Amount = 4 P

Then, Simple Interest = 4 P – P = 3 P.

**Formula-**

**Simple Interest = P x R x T/100**

**Where, P = principal , R = rate, & T = time.**

Then,

3 P = P x R x 15/100

3 = R x 3/20

R = 20

Hence, the answer is (3) 20 %.