SAT Math Multiple Choice Practice Question 531: Answer and Explanation

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Question: 531

9. The lengths of two sides of a triangle are 5 and 7. If the length of the third side is an integer, what is the least possible perimeter of the triangle?

A. 12
B. 13
C. 14
D. 15
E. 17

Correct Answer: D


D You know that any two sides of a triangle must add up to be larger than the third side. This means that whatever the third side of the triangle is, its value + 5 must be larger than 7. This means that the third side must be larger than 2. Because the question specifies that the third side has an integer value, the smallest integer larger than 2 is 3. So the third side will measure 3, and the perimeter will be 3 + 5 + 7 = 15.

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