SAT Question of the Day May 31st 2013

The stopping distance of a car is the number of feet that the car travels after the driver starts applying the brakes. The stopping distance of a certain car is directly proportional to the square of the speed of the car, in miles per hour, at the time the brakes are first applied. If the car’s stopping distance for an initial speed of 20 miles per hour is 17 feet, what is its stopping distance for an initial speed of 40 miles per hour?

A.     34 feet

B.     51 feet

C.     60 feet

D.     68 feet

E.     85 feet

Lets read the question and highlight the critical words:

The stopping distance of a certain car is directly proportional to the square of the speed.

That is – the distance equals a constant times the speed squared.

If we double the speed the distance of 17 feet would be quadrupled (2 square is 4) and will equal 68 feet.

38% out of 258,000 got it right.

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