If these two shapes are similar, what is the measure of the missing length u?

(Smaller triangle length: 60, 10 mm)
(Bigger triangle length: 66 mm, u)

To determine the measure of the missing length u, we can set up a proportion using the corresponding sides of the similar triangles:

60/10 = 66/u

Cross multiplying, we get:

60u = 660

Dividing by 60 on both sides, we get:

u = 660/60
u = 11

Therefore, the missing length u is 11 mm.