A small ring of negligible thickness and radius 2 cm moves on a bigger rung of radius 10 cm. How many rotations will the small ring take on the bigger ring to make a complete round ?

Solution (By Examveda Team)

Required number of rotations :
$$\eqalign{ & = \frac{{{\text{Circumference of bigger ring}}}}{{{\text{Circumference of smaller ring}}}} \cr & = \frac{{2 \times \pi \times 10}}{{2 \times \pi \times 2}} \cr & = 5 \cr} $$