
William W. answered 05/22/22
Experienced Tutor and Retired Engineer
If you re-draw the 3 triangles that are made, and put them side-by-side, you will see that this problem becomes easy:
Triangles 1 (the large blue one on the outside), 2 (the medium red on on the upper middle), and 3 (the smaller green one on the bottom middle) are similar triangles so their sides are proportional. Using Triangle #2 and Triangle #3, you can write proportional statements:
30 is to "x" like "x" is to 25 or:
30/x = x/25
Then cross multiply to get (30)(25) = x2
Then take the square root:
x = √(30•25)
Taking the square root of 25 gives you 5 so:
x = 5√30 cm