Most of us have little trouble working out how many milliliters are in 2.4 liters of water (it's 2,400). But the same can't be said when we're asked how many minutes are in 2.4 hours (it's 144).

I probably could have guessed that. What an interesting shop. NARRATOR: That’s a good idea, Fin. Arrange your credits into stacks of 10 to make them easier to count. 1 stack of 10… 2 stacks of 10.

NARRATOR: Yes, that is quite a hard sum. It might be easier if we separate the 17 into a 10 and a 7, and the 14 into a 10 and a 4. That gives us a 10, a 10, a 7 and a 4. Let's start by adding the ...