Similar figures

Two shapes, the same shape at two sizes. Every side of the big one is the matching small side times the same number. Pair the sides up first.

Use the pair you can see both of. 8 became 16, and 16 ÷ 8 = 2 — so every side is 2 times bigger.

Now the missing side is on the big shape, so multiply: 6 × 2 = 12.

It should be bigger than 6, and it is. So the missing side is 12 cm.