A circular running track has a diameter of 80 meters. A... | SAT Circles Question, Answer Explained

Math · Geometry and TrigonometryEasy

A circular running track has a diameter of $80$ meters. A runner completes $5$ laps around the track. To the nearest meter, how far does the runner travel?

$628$

$1{,}257$

$2{,}513$

$25{,}133$

Show answer and explanation

Answer: B

One lap is the circumference, $\pi d = 80\pi$ meters. Five laps is $5 \times 80\pi = 400\pi \approx 1{,}256.6$ meters, which rounds to $1{,}257$ meters.

Choice C uses $80$ as the radius in $2\pi r$ , but $80$ meters is the diameter.

Why the other choices are wrong

A. This uses π times the radius, 40, for each lap. The circumference is π times the diameter.
C. This uses 80 as the radius, but 80 meters is the diameter.
D. This uses the area of the circle instead of its circumference.

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