Chang knows one side of a triangle is 13 cm. Which set of two sides is possible for the lengths of the other two sides of this triangle?

For three lengths to form a triangle, the sum of any two sides must be greater than the third side. With sides 13 cm, 8 cm, and 9 cm, the two shorter sides add to 8 + 9 = 17 cm, which is greater than 13 cm; the other triangle inequalities also hold. So 8 cm and 9 cm are possible. The pairs in A and B add to exactly 13 cm, and C adds to less than 13 cm.

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