Question 34

Diameter of wheel of a cycle is 21 cm. The cyclist takes 45 minutes to reach a destination at a speed of 16.5 km/hr. How many revolutions will the wheel make during the journey?

Solution

Speed of cyclist = 16.5 km/hr , => In 60 minutes he covers = 16.5 km

=> In 45 minutes he covers = $$\frac{16.5}{60}\times45=12.375$$ km = $$1237500$$ cm

Radius of cycle = $$\frac{21}{2}$$ cm

Distance covered in 1 revolution = $$2\pi r$$

= $$2\times\frac{22}{7}\times\frac{21}{2}=66$$ cm

$$\therefore$$ Number of revolutions made by the wheel in the journey = $$\frac{1237500}{66}=18750$$

=> Ans - (B)

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