A wheel makes 2000 rounds when it covers a distance of 88 km. Find the radius of the wheel?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 7 m
In one round a wheel covers a distance equal to its circumference, \(2\pi r\). So the distance for one round is found first, and the radius from it.
The options are in metres, so the distance is changed to metres: 88 km \(=88000\) m
2000 rounds cover 88000 m, so one round covers \(88000\div2000=44\) m; this is the circumference
Setting the circumference equal to 44 m: \(\displaystyle 2\times\frac{22}{7}\times r=44\), that is \(\displaystyle \frac{44}{7}r=44\), so \(r=7\,\mathrm{m}\)