The wheels of a car is of diameter 80 cm each. How many complete revolutions does each wheel make in 30 mins when the car is moving at the speed of 66km/hr?
Answers
Radius of wheel= 80/2 = 40cm
∴ The distance travelled in one revolution is = 2πr = 2 x 22/7 x 40 = 1760/7 cm.
speed of car= 66km/hr= 66 x 1,00,000/60 cm/min = 1,10,000 cm/min.
distance covered by car in 1 min = 1,10,000cm
distance covered by car in 10min = 110,000 x 10 = 11,00,000cm.
number of complete revolution =
distance covered in 10min / distance covered in one revolution.
= 11,00,000/ 1760/7
= 11,00,000/1 x 7/1760 = 4375 revolutions.
Hence, in 10min each wheel of car makes 4375 revolutions.
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ExoticExplorerMaths AryaBhatta
Given diameter of the wheel = 80
So radius of the wheel r = 80/2 = 40
Now circumference of the wheel = 2πr
=2π*40
= 80π
Now Speed of the car = 66 km/hour
= (66*1000 *100)/60 (1 km = 1000m and 1 m = 100 cm, 1 hour = 60 minutes)
= (66*1000 *10)/6 (100 and 60 is divided by 10)
= 11*10000 (66 and 6 is divided by 6)
= 110000 cm/minute
Distance travelled by car in 10 minutes = 110000*10 = 1100000 cm
Let the number of revolution of the wheel is n.
So n*distance travelled in one minute = Distance travelled in 10 minutes
=> n*circumference of the wheel = Distance travelled in 10 minutes
=> n*80π = 1100000
=> n = 1100000/80π
=> n = (110000)/8π (1100000 and 80 is divided by 10)
=> n = (110000*7)/(22*8) (π = 22/7)
=> n = (10000*7)/(2*8) (110000 and 22 is divided by 11)
=> n = (5000*7)/8 (10000 and 2 is divided by 2)
=> n = 625*7 (5000 and 8 is divided by 8)
=> n = 4375
So number of revolution in 10 minutes at speed of 66 km/hour is 4375
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