Question

On a 246 km trip, a guy wants to achieve an average speed of 64.6 km/h. if she drives the first half of the trip at an average of 48.2 km/h, what average speed must she have for the second half of the trip?

Answer 1

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Answer 2

The required total time for the complete trip is
\[t _{total}=\frac{distance}{speed}=\frac{246}{64.6}\ hours\]
Time taken for the first half of the trip is
\[t _{1}=\frac{123}{48.2}\ hours\]
The time needed for the second half of the trip is given by
\[t _{2}=t _{total}-t _{1}=\frac{246}{64.6}-\frac{123}{48.2}=3.81-2.55=1.26\ hours\]
Therefore the average speed needed for the second half of the trip is
\[Required\ speed=\frac{123}{1.26}\ km/h\]