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Find the revolution per minute is required for the bus wheel with the diameter of 140 cm to make in order to keep a speed of 66kmph.

Option:
A. 125
B. 250
C. 400
D. 800
Answer: B . 250

Justification:

The bus speed S = 66 kmph = > S = 66 / 60 = 1.1 kmpm => S = 1100 meter per minute

The Perimeter of the bus wheel P = 2 * (22/7) * 70 = 440 cm.

Bus wheel covers 440 cm in one revolution => Number of revolution per minute = 1100 meter / 440 cm

=> N = 1100 * 100 / 440 = 250

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