9514 1404 393
Answer:
5 units
Explanation:
In this geometry, all of the triangles are similar. So, the ratio of short side to long side can be ...
x/10 = 10/4x
4x^2 = 100 . . . . . cross multiply
x^2 = 25 . . . . . . . divide by 4
x = 5 . . . . . . . . . . square root