SOLUTION: on her way home from work, luisa drives 10 miles through the city at about 30 mph and then 10 miles on the highway at about 50 mph. what is her average speed?

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Question 760558: on her way home from work, luisa drives 10 miles through the city at about 30 mph and then 10 miles on the highway at about 50 mph. what is her average speed?
Answer by Stitch(470) About Me  (Show Source):
You can put this solution on YOUR website!
To solve this problem you have to find out long Luisa was driving in both parts.
For her time in the city:
%281hour%2F30cross%28miles%29%29%2A%2810cross%28miles%29%2F1%29+=+0.333hours
For her time on the highway:
%281hour%2F50cross%28miles%29%29%2A%2810cross%28miles%29%2F1%29+=+0.2hours
So Louisa drove 20 miles in about 0.533 hours
20miles%2F0.533hours+=+37.5miles%2Fhour
Her average speed was 37.5mph.
** You may get more exact values by converting the hour to minutes