A circular running track lies between two circles with the same centre. The outer edge is 176 m round and the inner edge is 132 m round. What is the area of the track? Take $\pi = \frac{22}{7}$ .

154 m²Correct answerYour answer616 m²Correct answerYour answer1,078 m²Correct answerYour answer2,156 m²Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer C

Correct answer: C

Outer radius: $2\pi R = 176$ gives $R = 28$ m. Inner radius: $2\pi r = 132$ gives $r = 21$ m.
Track area = $\pi (R^2 - r^2) = \frac{22}{7} \times (784 - 441) = \frac{22}{7} \times 343 = 1078$ m².

Worth noting

154 m² squares the difference of the radii, $\pi(R - r)^2$ , which is not the same as $\pi(R^2 - r^2)$ .

Ten questions from Mensuration: Areas and Volumes, at your own pace.

A circular running track lies between two circles with the same centre. The outer edge is 176 m round and the inner edge is 132 m round. What is the area of the track? Take π=227\pi = \frac{22}{7}π=722​.