Question

a boy runs along the boundary of a circular field of radius 10m. after 10min he completed 3 rounds.what is the total distance he covered by him. also calculate his average speed​

Answer 1

Explanation:

As per the provided information in the given question, we have :

• A boy runs along the boundary of a circular field of radius 10m.
• He takes 10 minutes to complete 3 rounds.

We are asked to calculate the total distance travelled and average speed.

Suppose the boy starts from point A. So, distance covered in one round will be the perimeter or the circumference of the circular field. Then, 3 times the circumference of the circular field will be the total distance covered.

⇒ Total distance travelled = Distance travelled in 3 rounds

⇒ Total distance travelled = Distance travelled in 1 round × 3

⇒ Total distance travelled = Circumference × 3

⇒ Total distance travelled = 2πr × 3

⇒ Total distance travelled = 2 × $\sf \dfrac{22}{7}$ × 10 × 3 m

⇒ Total distance travelled = $\sf \dfrac{44}{7}$ × 10 × 3 m

⇒ Total distance travelled = $\sf \dfrac{440 \times 3}{7}$ m

⇒ Total distance travelled = $\sf \dfrac{1320}{7}$ m

∴ Total distance travelled is $\sf \dfrac{1320}{7}$ m.

Calculating average speed :

⇒ Average speed = Total distance ÷ Total time

• Total time = 10 minutes ⇒ 600

⇒ Average speed = ($\sf \dfrac{1320}{7}$ ÷ 10) m/min

⇒ Average speed = ($\sf \dfrac{1320}{7}$ × $\sf \dfrac{1}{10}$) m/min

⇒ Average speed = 18.85 m/min

∴ The average speed is 18.85 m/min.