Question

Given that the diameter of a ping pong ball is 40 mm and a tennis ball has a diameter of 6.8 cm, what is the ratio of the ping pong ball to the tennis ball.

Answer 1

6.8cm*10^2=680mm
40/680=1/17 is the ratio

Answer 2

First write them both with the same units, then compare.

1: convert both into mm
>> Ping pong = 40mm,
>> Tennis = 6.8*10=68mm

2. Compare
>> (Ping pong)/(tennis) = 40/68 = 10/17