Caroline drove 350 miles to her grandmother s house. The trip took her #5 1/4# hours. What was her average speed in miles per hour?

1 Answer
EZ as pi
Mar 13, 2018

#66 2/3# km per hour

Explanation:

The units of speed (km per hour) indicate which quantity you have to divide by which.

#"speed" = "distance"/"time"#

#=350 div 5 1/4#

#=350 div 21/4#

#=350 xx4/21" "larr# multiply by the reciprocal

#=cancel350^50 xx4/cancel21^3" "larr# cancel by #7#

#=200/3#

#=66 2/3# km per hour

As the question is given in fraction form it is better to answer in fraction form.

If you find the answer as a decimal it is #66.66666..# which is a recurring decimal. It can be rounded to #66.67# but then it is no longer accurate.
A fraction is exact.

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