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

The Correct Option is B

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