Question

Gavin had 20 minutes to do a three-problem quiz. He spent 9 3/4 minutes on Problem 1 and 3 4/5 minutes on Problem 2. How much time did he have left for Problem 3? Write the answer in minutes and seconds.
PS: Solve the problem using the RDW strategy. Show all of your work.

Answer 1

Add the time for the first two problems:

9 3/4 + 3 4/5

To add fractions rewrite them so they have a common denominator:

3/4 = 15/20

4/5 = 16/20

Now you have:

9 15/20 + 3 16/20 =  12 31/20 = 13 11/20 minutes.

Now subtract that from the time allowed:

20 - 13 11/20 = 6 9/20 minutes.