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Starting at home, Ishaan traveled uphill to the grocery store for 121212 minutes at just 151515 mph. He then traveled back home along the same path downhill at a speed of 303030 mph.

What is his average speed for the entire trip from home to the grocery store and back?

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 May 16, 2020
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I'm assuming this is a typo.

 

He traveled up for 12 min at 15mph, then went down 30mph. So if you are travelling at 30/15 = 2 times the speed your time is decreased by 2 times, so 12/2 = 6 minutes.

 

60/5 = 12 minutes at 15mph = 15/5 = 3miles. Similarly 60/10 = 6 minutes at 30 mph = 30/10 = 3 miles.

 

He travels a total of 6 miles in 12 + 6 = 18 minutes, so that's 1 per 3 minutes. 60/3 = 20, so 20*1 = 20 mph average speed.

 

If you odn't understand anything feel free to ask.

 May 16, 2020

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