Question

The area of a circular field is 616m.sq. Find the time taken by an athlete who completes 2 rounds if she is jogging at the rate of 5km/hr?

Answer 1

 Given : Area=616 m.sq
we know Area = (22/7) * R * R
            R * R = ( 616 *7) / 22
                     = 196
                  R = sq. Root(196)
                      =14
Now for 2 rounds we need to compute the distance

We Know Circumference = 2 * (22/7) *R
                                     =2 * (22/7) * 14
                                     =88 m for 2 rounds
                                     = 2 * Circumference
                                     = 2 * 88 = 176

We have now Distance = 176 m

Speed = 5km / hr
(Note to convert km/hr to m/s multiply by 5/18 )
                   Speed = (5 * 5)/18 =( 25/18 )       m/s
We have now Distance and Speed
To Find Time
 By Basic Physics Speed = Distance / Time
                        (ie) Time = Distance / Speed
                                      = 176 / (25 / 18 )
                                      = 126.72 seconds
                                      = 2.11 Minute