What is the time taken by Mohan to cover one round of a circular park of diameter 420 m, if he walks at a speed of 9 km/h ?

8.8 minutes

Diameter of a circular park = 420 m

Radius of a circular park = 210 m

Circumference of circle = 2Πr

= 2 × \(\frac{22}{7}\) × 210

= 1320 m

So , Distance = 1320 m

Speed = 9 km/h

9 km/h = 9  × \(\frac{50}{3}\) m/min = 150 m/min

Speed =150 m/min

 Time = \(\frac{Distance }{Speed}\) m/sec

 T = \(\frac{1320 }{150}\) m/sec

 T = 8.8 min

So , Time taken by a person to cover one round of circular park is 8.8 min.