Alice travels at an average speed of 60miles per hour from her home to a grocery store. She travels back to her home via same route at an average speed of 80 miles per hour. What is the average speed of her entire journey?
a)
b)
c)
70
d)
75
e)
82
Correct answer is option 'B'. Can you explain this answer?
Average speed = total distance / total time travel. in this case: let call the distance from home to grocery is x; then time to go from home to grocery is x/60; then time from grocery back home is x/80So average speed of entire journey = 2x / (x/60 +x/80) = 68,571
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Average speed = total distance / total time travel. in this case: let call the distance from home to grocery is x; then time to go from home to grocery is x/60; then time from grocery back home is x/80So average speed of entire journey = 2x / (x/60 +x/80) = 68,571