In triangle XYZ, the length of side XY is 23 mm and the length of side YZ is 36 mm. Which of the following could be the length of side XZ?

A.

11 mm

B.

61 mm

C.

64 mm

D.

43 mm

Answer: The correct answer is Choice D, 43 mm.

When you know 2 sides of a triangle, you can find the range for the final side of the triangle.

First, if we subtract 36 - 23 = 13, the third leg must be more than 13. Otherwise, the two smaller legs would not meet to make the third leg.

Second, if we add 36 + 23 = 59, the third leg must be less than 59. Otherwise, the third leg would reach further than the other two legs could reach.

43 is the only number larger than 13 but smaller than 59 in our list.