SAT Math : How to find the perimeter of an acute / obtuse isosceles triangle

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #2 : Isosceles Triangles

Two sides of an isosceles triangle are 20 and 30. What is the difference of the largest and the smallest possible perimeters?

Possible Answers:

10

15

30

The answer cannot be determined

0

Correct answer:

10

Explanation:

The trick here is that we don't know which is the repeated side. Our possible triangles are therefore 20 + 20 + 30 = 70 or 30 + 30 + 20 = 80.  The difference is therefore 80 – 70 or 10.

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