Stella and Michael are helping their friend Austin move. Stella can move one box for every four boxes that Michael can move. If Stella moves ten boxes, how many boxes can Michael move?

Explanation:

Stella can move 1 box for every 4 boxes Michael moves.

She moves 10 boxes, so that must mean Michael moved 40 boxes (since 4*10 = 40).

Put another way, the ratio 1:4 bumps up to the equivalent form 10:40 after multiplying both parts by 10. The first value of each ratio is the amount of boxes Stella moves, and the second part is what Michael moves.

You could also solve it like this

1/4 = 10/x

1*x = 4*10

x = 40

In the second step, I used cross multiplication.