Digital PSAT Math Practice Question 159: Answer and Explanation

Question: 159

Six identical isosceles triangles are arranged as shown in the figure above. If one side of each triangle has length a and if the other two sides each have length b, what is the outside perimeter of the figure above in terms of a and b?

• A. 4a + 4b
• B. 6a + 2b
• C. 6a + 7b
• D. 6a + 12b

Correct Answer: B

Explanation:

(B) Notice that the top and bottom sides each have a length of 3a, while the left and right sides will each have a length of b. Therefore, P = 3a + b + 3a + b. Combine like terms:

The answer is choice (B).