Question

In a Racing Championship of a $3$-lap race, where the race track is in the form of a circle of radius $R$, find the total length in metres which a contestant needs to run in the race.

• A. $3R$
• B. $3\pi R$
• C. $3\pi R^2$
• D. $6R$
• E. $6\pi R$

Answer 1

Answer: (E)

$6\pi R$

Since the radius of the circular race track is $R$ and there are $3$ laps in the racing championship, therefore the radius becomes $3R$.

Now as we know the circumference of the circle is given by $C=2\pi r$,

Hence, the total length which a contestant needs to run in the race is:

$2\pi r=2\pi \left(3R\right)=6\pi R$