Question

the diameter of the cycle wheel is 21cm.how many revolutions will it make to travel 1.98km?

Answer 1

The diameter = 21 cm

Radius= 21/ 2= 10.5 cm

So the circumference = 2 * pi * r= 2* 22/7 * 10.5 = 66 cm

Now we know that 

Total no. of revolutions= Distance to be travelled/ Circumference of wheel

=  (1.98 * 1000 * 1000)/ 66   { Converting km to cm }

= 198000/ 66

=3000 revolutions

Answer 2

Given that the diameter of wheel = 21cm.

Then the radius of the wheel r = d/2 = 21/2 = 10.5.

We know that circumference of the wheel = 2pir

                                                                       =  2 * 22/7 * 10.5

                                                                       = 66cm.

Given that distance to be covered = 1.98km.

                                                           = 198000 cm.

Therefore number of revolutions = 198000/66

                                                       = 3000.


Hope this helps!