Question

a circular track has a radius of 140m A boy runs on this track at a speed of 8.8km/h.How long will it take for him to run 12 rounds of the track​

Answer 1

Distance to be covered to complete 1 round of the track = 2 × 22/7 × radius = 2 × 22/7 × 140

= 2 × 22 × 20 = 880 m

Distance to be covered to complete 12 rounds

= 880 × 12 m

Time taken = distance to be covered / speed

= 880 × 12 / 8.8 × 1000

= 880 × 12 / 8800

= 12 / 10

= 1.2 hours

Answer 2

Answer:

1 hour 12 mins

Step-by-step explanation:

Find the distance of 1 round of the track:

Circumference = 2πr

Circumference = 2π(140)

Circumference = 280π m

Find the distance of 12 rounds of the track:

1 round = 280π m

12 rounds = 280π x 12 = 10560 m = 10.56 km

Find the time needed:

Speed = 8.8 km/h

8.8 km = 1 hour

10.56 km = 1/8.8 x 10.56

10.56 km = 6/5 hour = 1 hour 12 mins

Answer: 1 hour 12 mins