Question

From home to school, Armen spent 36 minutes walking at a speed of 70 yards per minute. What was his speed, if he spent 8 minutes less time while getting back?

Answer 1

90 yards per minute

Explanation:

Armen's time getting back was 36 -8 = 28 minutes. Then the ratio of times is 28/36 = 7/9.

The ratio of speeds is the inverse of this, so his speed coming back is ...

speed/70 = 9/7

Multiplying by 70 gives ...

speed = 70·9/7 = 90 . . . . yards per minute