Mathematics
What is the cross-sectional area of the head of a piston that has a diameter of 6 inches? (Use pi = 3.1416)
Answer
28.27 square inches
Area of a circle = pi x r^2. The radius is half the diameter, so r = 3 in, and A = 3.1416 x 3^2 = 3.1416 x 9 = 28.27 sq in. 18.85 is the circumference (pi x D), not the area. 113.10 comes from squaring the diameter instead of the radius (pi x 6^2), a very common mistake. 9.42 is pi x r, which is neither area nor circumference.
Source: FAA-H-8083-30B (AMT Handbook-General), Ch. 3 Mathematics - Area of a Circle
Not the answer
- 9.42 square inches
- 18.85 square inches
- 113.10 square inches
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