Question

How can I find the missing length for the triangles in each pair are similar

Answer 1

If these two triangles are mathematically similar, then we know angle A on the smaller triangle is the same as angle A on the bigger triangle.

That means it's safe to assume if you flipped the triangle around to make it so that C = W and B = V (as shown in the picture)

That means you can do 16 / 8 to find the scale factor, as the lengths are similar, so the scale factor is 2.

Apply the same logic to the 20cm length, and do 20 / 2 (the scale factor) to get 10cm for the smaller length.

Answer 2

In similar triangles, the sides are proportional. If we look at the sides that are 8 and 16, the side that is 8 is multiplied by 2 to get 16. So the scale factor is 2. Therefore we do 20/2 to get 10 which is the unknown side

Hope this helps. Let me know if you need more help