Question 1186142
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A car travels 20 miles in 30 minutes.
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"A car"  travels at the speed of 40 miles per hour.



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If Mike drives the first 5 miles at 20 mph
How fast is he driving the remainder of the trip?
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Is Mike driving "A car"?
That car travels at 40 mph, not at 20 mph.
The description for Mike and his travel is incomplete.




Maybe your exercise description was supposed to be like this:
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Mike drives the first five miles of a 20 mile trip at 20 mph.  How fast does he drive the remainder of this trip?
<pre>
               SPEEDS      TIME in Hours        MILES DISTANCE

FirstPart        20        5/20=1/4                 5

Remainder                  1/2-1/4=1/4           20-5=15

TOTAL                         1/2                 20
</pre>
The missing speed for the "Remainder" of the trip is  {{{(15*miles)/((1/4)*hours)}}}
or 60 mph.