The radius of a wheel is 0.25 m. The number of revolutions it will make to travel a distance of 11 km will be
(a) 2800
(b) 4000
(c) 5500
(d) 7000
We have given the radius of the wheel that is 0.25 cm.
We know that distance covered by the wheel in one revolution $=\frac{\text { Distance moved }}{\text { Number of revolutions }}$.
Distance covered by the wheel in one revolution is equal to the circumference of the wheel.
$2 \pi r=\frac{\text { Distance moved }}{\text { Number of revolutions }}$......(1)
Distance moved is given as 11 km so we will first convert it to m.
$\therefore 11 \mathrm{~km}=11000 \mathrm{~m}$
Now we will substitute the values in equation (1),
$2 \times \pi \times 0.25=\frac{11000}{\text { Number of revolutions }}$
Now we will substitute $\pi=\frac{22}{7}$.
$2 \times \frac{22}{7} \times 0.25=\frac{11000}{\text { Number of revolutions }}$
Simplifying equation (1) we get,
Number of revolutions $=\frac{11000 \times 7}{2 \times 22 \times 0.25}$
$\therefore$ Number of revolutions $=\frac{11000 \times 7}{22 \times 0.5}$
$\therefore$ Number of revolutions $=\frac{1000 \times 7}{2 \times 0.5}$
$\therefore$ Number of revolutions $=\frac{7000}{1}$
$\therefore$ Number of revolutions $=7000$
Therefore, it will make 7000 revolutions to travel a distance of $11 \mathrm{~km}$.
Hence, the correct answer is option $(d)$.