Question

The diameter of a cycle wheel is 70 cm. A cyclist takes 30 hours to reach a destination at the speed of 22 km/hr. How many revolutions will the wheel make during this journey?

• A. 3 million
• B. 3 lakh
• C. 4 lakh
• D. None of these

Answer 1

Answer: (B)

3 lakh

Answer 2

From the question we know that,

The Distance covered at 22 $\frac{km}{hr}$ in 30 hours = 22 × 30 = 660 km = 66 × 106 $cm$

The radius of a cycle wheel = 35 cm $(\frac{70}{2})\ cm$ as 70 is diameter

In one revolution, the distance covered by the wheel will be equal to the Circumference of cycle wheel

Circumference of cycle wheel = $2 \pi r$

= $2 \times \frac{22}{7} \times 35 = 220\ cm$

Now, The Number of revolutions in the total journey = $\frac{66 \times 10^6}{220}$ = 3 × 105

= 300000

The correct option is (B): 3 lakh