There are actually 2 ways to get this answer - the first one is mine and the second is another's.
The way I did it was I divided 40 / 2, which is 20. I then did 60 (an hour) / 20, which is 3. How can we make sure of this? Well, that's where the other way comes in.
The other way to do this (originally posted by HomertheGenius) is to do 2 / 40, which is 0.05, and if we figure out what 0.05 of an hour is (do 0.05 x 60), we get 3 minutes.
With both methods, we can easily prove that it would take 3 minutes. Hope I could help (even though I'm 4 hours late...)!
rrriok, the house of... idk