Express the following as a unit rate.  If necessary round to the nearest tenth.  100 miles in 2.5 hours.

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100 miles in 2.5 hours

We need to find the speed (or how many miles in an hour)

The speed S = distance D / time T

       S = 100/2.5 = 40 mile/hour

Or if we use the ratio properties:

100 miles in 2.5 hour

  x   miles in 1 hour

2.5 * x = 100* 1

 ==> x= 100/2.5 = 40 m/h

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You can express this as 40 miles per hour.

We know that we have gone 100 miles and that it took us 2.5 hours to go that distance.  All we have to do to find out how many miles per hour this is is to divide the number of miles gone by the number of hours it took to go that distance.

So we divide 100 by 2.5 and we get 40.

One way to remember what you have to do here is to realize that the word "per" means "divided by."  So if you have miles per hour, you take the number of miles (100) and divide them by the number of hours (2.5) and get miles per (divided by) hour.

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