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On his trip to the mountains, Klink drove for 3 hours at an average speed of 50 mph, then for 2 hours at an average speed of 30 mph. What was his average speed for the entire trip?

Answer 1

Emily Abbate

The average speed was 42 mph.

3 hours at an average speed of 50 mph:

The distance driven during those 3 hours would be #50 "miles"/cancel("hour") * 3 cancel("hours") = 150 "miles"#

2 hours at an average speed of 30 mph:

The distance driven during those 2 hours would be #30 "miles"/cancel("hour") * 2 cancel("hours") = 60 "miles"#

The total miles driven was 210 miles. The total elapsed time was 5 hours. Therefore the average speed was

#"average speed" = "total miles"/"total elapsed time"#

#"average speed" = (210 "miles")/(5 "hours") = 42 "mph"#

Tip: The point of "average speed" is that in this case, driving at 42 mph for 5 hours would take him 210 miles.

I hope this helps, Steve

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