ISEE Mathematics Achievement Question 91: Answer and Explanation
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Question: 91
7. A board 30' long is cut into three unequal parts. The first is three times as long as the second. The third is twice as long as the first. How long is the longest piece
- A. 6'
- B. 9'
- C. 12'
- D. 18'
Correct Answer: D
Explanation:
The correct answer is (D). Note that the second piece is the shortest. We don't know its exact length, so call it x feet long. The first piece is three times as long as the second, or 3x feet long. The third is twice as long as the first, or 6x feet long. All the pieces total x + 3x + 6x = 10x feet. The board is 30 feet long, and the pieces are 10x feet long. 10x = 30, so x = 3, which is the length of the shortest piece. The largest piece is six times the shortest, or 18 feet long.