Answer:
B. 30 in, 40 in, 50 in
Explanation:
You can try all of these combinations of side lengths in the Pythagorean theorem, or you can make use of your knowledge that the side ratios 3:4:5 form a right triangle. Only selection B (30, 40, 50) has the side lengths in that ratio.
If two of the 3 numbers have those ratios, but the third one doesn't agree, then the triangle will not be a right triangle.
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Check
50^2 = 30^2 + 40^2 . . . . . the square of the hypotenuse is the sum of the squares of the two legs for a right triangle
2500 = 900 + 1600 . . . . . true
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Attached is a graph showing the various triangles. Only the one with the dimensions of B is a right triangle.