Maths Olympiad Prep

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Geometry Difficulty 3.1 AMC 10/12 Find the answer

Riders on a Ferris wheel travel in a circle in a vertical plane. A particular wheel has radius 2020 feet and revolves at the constant rate of one revolution per minute. How many seconds does it take a rider to travel from the bottom of the wheel to a point 1010 vertical feet above the bottom?

Pick one

Solution

We can let this circle represent the ferris wheel with center O,O, and CC represent the desired point 1010 feet above the bottom. Draw a diagram like the one above. We find out OBC\triangle OBC is a 30609030-60-90 triangle. That means BOC=60\angle BOC = 60^\circ and the ferris wheel has made 60360=16\frac{60}{360} = \frac{1}{6} of a revolution. Therefore, the time it takes to travel that much of a distance is 16th\frac{1}{6}\text{th} of a minute, or 1010 seconds. The answer is (D) 10\boxed{\mathrm{(D) \ } 10}. Alternatively, we could also say that ABC\triangle ABC is congruent to OBC\triangle OBC by SAS, so ACAC is 20, and AOC\triangle AOC is equilateral, and BOC=60\angle BOC = 60^\circ

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.