Question

Ram goes for a morning walk in a circular park daily . He completes one revolution of the park in 4minutes .find his speed if the diameter of the park is 420 m.

Answer 1

DIAMETER = 420 m

 RADIUS = 420 / 2 = 210 m

DISTANCE COVERED IN 1 REVOLUTION = CIR. OF CIRCLE

                                                                = 2 * 22/7 * r

                                                                = 44/7 * 210

                                                                 = 1320 m

TIME TAKEN = 4 minutes = 4 * 60 s = 240 s

 SPEED  = DISTANCE / TIME

               = 1320 / 240 

               = 5.5 m/s

Answer 2

it's very simple...
r=half of diameter
r=210
circumference of circle=2*22/7*210
=44*30=1320
then we have dist.,time...so we can find speed