a car has wheels which are 80 CM in diameter how many complete revolutions does each wheel makes in 10 minutes when the car is travelling at the speed of 66 km per hour
Answers
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
Hope This helps :)