Answers:
(a) 15
(b) 6.5
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Work Shown
Part (a)
Use a bit of trial-and-error to notice
36 = 12*3
39 = 13*3
Meaning that a right triangle with leg 12 and hypotenuse 13 has been enlarged by a scale factor of 3. In other words, the sides have been tripled.
The pythagorean triple 5-12-13 will then be used to determine the missing side is 5*3 = 15.
Answer to part (a) is 15
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Part (b)
Again we'll need trial-and-error if we cannot use a calculator.
Double each side of the triangle shown.
2.5*2 = 5
6*2 = 12
We have another 5-12-13 right triangle.
The missing side must be 13/2 = 6.5
Answer to part (b) is 6.5