SOLUTION: Danielle drives from her home to the store at an average speed of 40 miles per hour. She returns home along the same route at an average speed of 60 miles per hour. What is her av

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Question 495304: Danielle drives from her home to the store at an average speed of 40 miles per hour. She returns home along the same route at an average speed of 60 miles per hour. What is her average speed, in miles per hour, for the entire trip The way the book explained how they got 48 im confused would some one break this problem down word from word for me
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Danielle drives from her home to the store at an average speed of 40 miles per hour.
She returns home along the same route at an average speed of 60 miles per hour.
What is her average speed, in miles per hour, for the entire trip?
:
Here is one way that is pretty easy to understand
Let a = average speed for the entire trip
Let d = the one-way distance
:
Write a time equation, time = dist/speed
:
to store time + return time = total time
d%2F40 + d%2F60 = %282d%29%2Fa
multiply by 120a to get rid of the denominators, results
3ad + 2ad = 120(2d)
5ad = 240d
we don't need d, divide both sides by d, leaving us with
5d = 240
d = 240%2F5
d = 48 mph,
:
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How about this? Did it make sense to you?