RS Aggarwal - Mathematics

Book: RS Aggarwal - Mathematics

Chapter: 18. Area of Circle, Sector and Segment

Subject: Maths - Class 10th

Q. No. 31 of Exercise 18B

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31

The wheels of the locomotive of a train are 2.1 m in radius. They make 75 revolutions in one minute. Find the speed of the train in km per hour.

Given radius of wheel = R = 2.1m


Number of revolutions in one minute = 75


Number of revolutions in 1 hour = 75×60


Number of revolutions in 1 hour = 45000


Distance covered in one revolution = Circumference of wheel


Distance covered in 1 revolution = 2πR (where R = radius of wheel)


Distance covered n 1 revolution = 2π(2.1)



= 13.2 m


So, distance covered in 4500 revolutions = 4500×distance covered in 1


Distance covered in 4500 revolution = 4500× 13.2


Distance covered in 4500 revolutions = 59400 m = 59.4 km


Distance covered in 1 hour = 59.4 km


Hence speed of the locomotive = 59.4 km/hr


The speed of locomotive is 59.4 km/hr


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