The Length of the Second Train

A train moving at a speed of 49 mph is passed by a train moving at a speed 63 mph.

A passenger in the first train noted that the second train took 4.5 seconds to pass

How long is the second train?

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1. The relative velocity between the trains is 112 mph (63 + 49).
2. To get the answer we must multiply the velocity times the time.
3. To get the correct units, convert mph to feet per sec, then multiply times 4.5 sec to get the answer in feet.

Answer: (5289 x (49 + 63) x 4.5) / (60 x 60) = 740.46 feet.

The length of the second train is ‘740.46’ feet

The Driving School

A driving school claims an average test pass rate of 76.8 per cent.

What is the least number of pupils required to achieve this result?

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The answer is 125 as we need 96 passes out of 125 to get an average of 76.8%