exam Maths Puzzle Numerical Ability

A driver sets out on a 20-mile trip. When he has gone halfway he finds he has averaged 25 mph. At what speed must he travel the rest of the way to make his overall average speed for the trip 40 mph?

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exam Other Question

A regular has an exterior angle which equals 36 degrees.
how many sides has this regular polygon got? A moving walkway at an airport is 65.0 m long. A child runing at a constand speek takes 20.0 s to run along the walkway in the direction it is moving, and then 52.0 s to run all the way back. What are the speed of the walkway and the speed of the child?