The wheels of a car are of diameter 80 cm each. How many complete revolutions does each wheel make in 10 minutes when th

Question

The wheels of a car are of diameter 80 cm each. How many complete revolutions does each wheel make in 10 minutes when the car is travelling at a speed of 66 km/h?

Accepted Answer

Diameter $d = 80$ cm, radius $r = 40$ cm. Circumference $= 2 	imes \frac{22}{7} 	imes 40 = \frac{1760}{7}$ cm. Speed $= 66	ext{ km/h} = \frac{66 	imes 100000}{60}	ext{ cm/min} = 110000	ext{ cm/min}$. Distance in 10 minutes $= 110000 	imes 10 = 1100000$ cm. Number of revolutions $= \frac{1100000}{1760/7} = \frac{1100000 	imes 7}{1760} = 4375$.

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