# Solve for the unknown number of years in each of the following: a) Principal amount = 500, Interest rate = 8%, Simple interest = 400, b) Principal amount = 100, Interest rate = 10%, Simple interest = 550.

Simple interest is very interesting concepts which have many practical applications in real life. Many of the money matters are solved using formulae related to this concept. Let's solve some problems so that you can be comfortable handling your money!

## Answer: For Principal amount = 500, Interest rate = 8%, Simple interest = 400, The number of years is 10, and for Principal amount = 100, Interest rate = 10%, Simple interest = 550, the number of years is 55.

Let's understand how we arrived at the solution.

**Explanation:**

We use the formula to calculate simple interest to solve the problems:

⇒ (Principal × Years × Interest Rate) / 100 = Simple Interest

a) In this case, after we substitute the values in the formula:

⇒ (500 × Years × 8) / 100 = 400

⇒ Therefore, Years = 10

b) In this case, after we substitute the values in the formula:

⇒ (100 × Years × 10) / 100 = 550

⇒ Therefore, Years = 55