Answer: Choice B
15 + 5*sqrt(3)
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How to get this answer:
Let A, B, C be the sides of the triangle such that A < B < C.
A is the short leg, B is the long leg, C is the hypotenuse
For any 30-60-90 triangle, the hypotenuse is twice as long as the short leg, so
C = 2*A
C = 2*5
C = 10
For any 30-60-90 triangle, the long leg is exactly equal to sqrt(3) times the short leg
B = A*sqrt(3)
B = 5*sqrt(3)
Now add up the three sides
A+B+C = 5+5*sqrt(3)+10
A+B+C = 15+5*sqrt(3)