If Marcus can type 40 words in half a minute, then 40 times 2 equals 80. 80 words a minute for Marcus. If Rhys can type 100 words in 1 1/2 minute, 100/ 1.5 = 66.66 and 80>66.66 so Marcus can type a greater rate of words per minute.
Well, it would end up taking Sandy 3 minutes to run the race and Chris 2 and a half minutes. Meaning Sandy crossed the Dubinsky line 30 seconds after Chris.
