Answer:
b = 20
Explanation:
This is a right triangle with the ratio of the given sides being ...
15 : 25 = 3 : 5
This means it is a 3:4:5 right triangle. The side ratios are ...
a : b : c = 3 : 4 : 5 = 15 : 20 : 25
The missing side length is b = 20.
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You can also figure this using the Pythagorean theorem.
c² = a² + b²
25² = 15² +b²
625 -225 = b² = 400
b = √400 = 20
The missing side length is 20.