ISEE Mathematics Achievement Question 63: Answer and Explanation
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Question: 63
7. Find the diameter of a circle whose area is 78.5 sq. in.
- A. 25 feet
- B. 10 feet
- C. 25 inches
- D. 10 inches
Correct Answer: D
Explanation:
The correct answer is (D). The area of a circle is found by A = πr2. The radius is half the diameter. To find the diameter when the area is known, divide the area by π to find the square of the radius.
78.5 ÷ 3.14 = 25
Since the square of the radius is 25, we know the radius is 5, and the diameter is twice the radius, or 10 inches.