The wheels of a car are of diameter 80 cm each. How . . .

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 per hour?

Doubt by Ziya

Video Solution : 

Text Solution : 

Diameter (d) = 80 cm
radius (r) = d/2 = 80/2 = 40 cm

Time (t)
= 10 minutes
= 10×60 seconds
= 600 seconds

Speed
= 66 km/h
= [66×1000×100]/[60×60] = 11000/6 cm/s

Now, Speed = Distance/Time
Distance = Speed×Time
Distance = (11000/6)×600 = 1100000 cm 

Number of revolutions
= Total Distance covered / Distance covered in one revolution
= Total Distance / Circumference 
= 1100000/[2×(22/7)×40]
= (110×100×100×7)/(44×40)
= (100×100×7)/(4×4)
= 25×25×7
= 625×7

= 4375

Hence, in 10 minutes wheel will make 4375 revolutions.