You earn $10.00/hour. You invest $4,000.00 at an interest rate of 5% APR for a year. How much interest did that savings earn in a year in terms of hours of work?

A. 100 hours

B. 20 hours

C. 40 hours

D. 400 hours

Where:

P is the principal amount, $4000.00. r is the interest rate, 5% per year, or in decimal form, 5/100=0.05. t is the time involved, 5 ... year (s) time periods. So, t is 5 ... year time periods. To find the simple interest, we multiply 4000 * 0.05 * 5 to get that:

The interest is: $1000.00 / 5 = $200/$10=20 Hours