Question

A man runs round a circular field of radius 50m at a speed of 12km/hr.What time is taken by man to make 20 rounds of the field??

Answer 1

circumference =2pie r
2×22/7×50=314.28m
20 rounds = 314.28×20=6285.6m
or 6.285km
time=6.285/12
0.52 hrs

Answer 2

in 1st round circular field distance =
$2\pi \times r$
so distance=2×3.14×50
=312 m
so 20 round distance of circular field =20×312
=6240
from formula, time=distance/speed
so time=6240/12
=520 second
or 8.66 minutes