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?

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Answers

Linh Nguyen
Aug 27, 2019
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/80

So average speed of entire journey = 2x / (x/60 +x/80) = 68,571

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
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