The minute arm of a clock is 10 cm long. The number of minutes taken by the tip of the arm to travel a length of 10 cm is nearly equal to
(a)5
(b)10
(c)15
(d)20
Answer
Answer (as printed): B
Explanation
Distance covered by the arm tip in 1 round $$=\left(2 \times \frac{22}{7} \times 10\right) \mathrm{cm}=\frac{440}{7} \mathrm{cm} .$$ Now, $\frac{440}{7} \mathrm{cm}$ is covered in 60 min . $$\begin{aligned} & \therefore 10 \mathrm{cm} \text { is covered in }\left(60 \times \frac{7}{440} \times 10\right) \mathrm{min} \\ &=9.54 \mathrm{min} \approx 10 \mathrm{min} . \end{aligned}$$