Which of the following are not the lengths of the sides of a 30°-60°-90° triangle?

Answer:
B. 5/2, 2√3/2, 10
Step-by-step explanation:
A 30-60-90 triangle must have their sides equal to x, x√3, and 2x, where x represents one of the sides.
Let's say x is 5/2, (5/2)√3 is (5√3)/2. So far this side works for a 30-60-90 triangle. But 2x would be 5/2(2) = 5.
This means the other side should be 5, not 10. Therefore this triangle cannot be a 30-60-90 triangle.
You can see that in all of the other answers, the second number is the first number times √3, and the third number is the first number times 2.