A roller has a diameter of 1.4 m. Find :

(i) its circumference

(ii) the number of revolutions it makes while traveling 61.6 m.

(i) Given:

Diameter of roller = 1.4 m

Radius = $\dfrac{\text{Diameter}}{2}$

= $\dfrac{1.4}{2}$ m

= 0.7 m

As we know, the circumference of the circle = 2πr

$2 \times \dfrac{22}{7} \times 0.7\\[1em] = \dfrac{44}{7} \times 0.7\\[1em] = \dfrac{30.8}{7}\\[1em] = 4.4 \text{ m}$

Hence, the circumference of the roller is 4.4 m.

(ii) Let the roller make a revolutions while traveling 61.6 m.

Distance travelled by roller in a revolutions = Circumference of the wheel x a

⇒ 61.6 = 4.4 x a

⇒ a = $\dfrac{61.6}{4.4}$

⇒ a = 14

Hence, the roller makes 14 revolutions while traveling 61.6 m.