The wheel of a motor cycle is of radius 35 cm. How many revolutions per minute must the wheel make, so as to keep a speed of 66 km/h?
Radius of wheel = r = 35 cm
1 revolution of the wheel = Circumference of the wheel
= 2πr
= 2 × (22/7) × 35
= 220 cm
But Speed of the wheel = 66 km/hr
= 
cm/min
= 110000 cm/min
∴ Number of revolutions in 1 min = 110000/220 = 500
Hence, required number of revolutions per minute is 500.
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