Liz ran 32 mi, 11 mi, and 20 mi during three weeks. How many miles must she run the fourth week to give her an average of 20 miles per week?

Answer 1

Hi! You need to solve for x and this can be done by creating a ratio

32 + 11 + 20 +x

------------------------=20

4

We divide by 4 because we are looking at averages for 4 weeks.

63 + x 20

----------- = -----

4 1

Multiply 63+x by 1 and 20 by 4

80=63 + x

-63 -63

---------------

17=x

To check work:

32 +11+20+17=80

80/4=20

Hope that helps!