Question

how would a boy take to walk once round a circular park whose diameter is 420m if his speed is 3 km per hour

Answer 1

Given diameter = 420m. Then the radius will be r = 210m.

Circumference = pi * d

                         = 22/7 * 420

                         = 1320 m

                         = 1.32km


Time taken = 1.320/3 (Given speed = 3 km/hr)

                   = .44 hr
      
                   = 26.4 minutes.


Hope this helps!

Answer 2

Answer:

0.44hr or 26.4 min

Step-by-step explanation:

Circumference= 2*22/7*radius

Radius=420/2=210

Circumference= 2*22/7*210m

                        =2*22*30 [7 and 210 cancel]

                        =1320m

Time= Distance/Speed

1320m/ 3km per hour or 3000m per hour

1320/3000= 0.44hr