 Hi and welcome to the session. Let us discuss the following question. Question says, 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? First of all let us understand that distance covered by the wheel in one revolution is equal to circumference of the circle or we can say circumference of the wheel. And we know circumference is equal to 2 pi multiplied by radius of the circle. Let the radius of the wheel be r then distance covered by the wheel in one revolution is equal to 2 pi r. Let us represent the distance covered by the wheel in one revolution by d then d is equal to 2 pi r. This is the key idea to solve the given question. Let us now start with the solution. We are given diameter of the wheel it is equal to 80 cm. Now we know radius of the wheel is equal to half of diameter. So we can write radius of wheel that is r is equal to 80 upon 2 or we can say r is equal to 40 cm. Now we will find out circumference of the wheel. We know circumference of the circle is equal to 2 pi multiplied by radius of the circle. So circumference of the wheel is equal to 2 pi r. We know radius of the wheel is r. Now value of r is equal to 40 cm. So substituting 40 for r in this expression we get 2 multiplied by 22 upon 7 multiplied by 40 is equal to circumference of the wheel. Now simplifying further we get circumference of the wheel is equal to 1760 upon 7 cm. Now we will find out total distance covered by the car. We know speed of the car is equal to 66 km per hour time for which the car travels is equal to 10 minutes which is further equal to 10 upon 60 hours. Now let us find out distance travelled by the car in 10 minutes. We know distance is equal to speed into time. So distance travelled by the car in 10 minutes is equal to 66 multiplied by 10 upon 60 km. Now this is further equal to 66 multiplied by 10 upon 60 multiplied by 1000 meters. We know 1 km is equal to 1000 meters. So we will multiply this term by 1000 to convert it into meters. Now simplifying further we get distance covered by the car in 10 minutes is equal to 11000 meters. Now we also know that total distance travelled by the car in 10 minutes is equal to total number of revolutions made by the wheel multiplied by distance travelled in 1 revolution. So we can write total number of revolutions multiplied by distance travelled in 1 revolution is equal to total distance travelled by the car. Now this implies total number of revolutions made by the wheel is equal to total distance travelled by the car in 10 minutes upon distance travelled by the car in 1 revolution. Now we know total distance traveled by the car is equal to 11,000 meters and distance traveled in one revolution is equal to 1760 upon 7 centimeters which can be further written as 1760 upon 700 meters so we can write 11,000 upon 1760 upon 700. Now simplifying this expression further we get total number of revolutions made by the wheel is equal to 11,000 multiplied by 700 upon 1760. Now 0 will get cancelled by 0 we know 11 multiplied by 1000 is equal to 11,000 and 11 multiplied by 16 is equal to 176 now we will cancel common factor 8 from numerator and denominator both we know 8 multiplied by 2 is equal to 16 and 8 multiplied by 125 is equal to 1000. Now we will cancel common factor 2 from numerator and denominator both we know 2 multiplied by 35 is equal to 70 now this is further equal to 4375. So total number of revolutions made by the wheel is equal to 4375 so we can write total number of revolutions made by each wheel is equal to 4375 so 4375 is our required answer this completes the session hope you understood the solution take care and have a nice day.