# Finding the Time Period for Compound Interest

by Nirmal

(Dubai)

**Question**

in what time the compound interest on Rs800 at 20% per annum will amount to Rs1152 if compounded annually?

**Answer**

**STEP 1**The compound interest formula is given below:

Where:

- A is the total amount of money (including interest) after n years

- P is the principal (the amount money borrowed or invested)

- r is the interest rate (per year or per annum)

- n is the loan or investment duration in years

**STEP 2**Thus, let us substitute the values we have into the formula:

1152 = 800(1+0.2)^n

**STEP 3**We can then proceed to solve the equation:

1152/800 = (1.2)^n

1.44 = (1.2)^n

1.44 = (1.2)^2

Thus, it takes

**two years** for the compound interest to amount to Rs1152.

You can also refer to our tutorial on

how to calculate compound interest.