intrest problem

[romitvsingh]

Ann invested a certain sum of money in a bank that paid simple interest. The amount grew to $240 at the end of 2 years. She waited for another 3 years and got a final amount of $300. What was the principal amount that she invested at the beginning?

[VivianKerr]

After 2 years it was $240, and after 3 more years it was $300, so we know in 3 years it grew by $60, so each year it grew by $20.

So in the first two years it grew $20 per year, a total of $40.

$240 - $40 = $200.