Multiple choice

Radius of a circular field is 70 m. How much time will it take to go twice around the field with a speed of 4 km/hr?

  1. 7 hours 7 minutes

  2. 13 minutes 20 second

  3. 13 minutes 12 seconds

  4. 7 hours 42 minutes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Radius = 70m. Circumference = 2 * pi * 70 = 440m. Twice around = 880m. Speed = 4 km/hr = 4000/3600 m/s = 10/9 m/s. Time = 880 / (10/9) = 88 * 9 = 792 seconds. 792 seconds = 13 minutes and 12 seconds.

AI explanation

First, find the total distance to travel twice around the field by calculating the circumference using the formula 2 times pi times radius, which is 2 times 22 over 7 times 70 metres, equaling 440 metres for one round. Doubling this gives a total distance of 880 metres, which converts to 0.88 km. Using the Time equals Distance over Speed formula, divide 0.88 km by 4 km/hr to get 0.22 hours, which converts to 13 minutes and 12 seconds.

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