Question

a rectangular field is 72 m by 58 m. A girl walks around 8 at the rate of 3 km per hour how long it will take to make 3 rounds.

Answer 1

l = 72 m, b = 58 m
as perimeter = 2(l+b)
therefore p = 2 ( 72 + 58 )
= 2(130)
= 260 m
therefore 3 rounds covers 3*260 = 780m
speed of girl = 3 km/hr = 3000m/60min
therefore time required is
$\frac{60 \times 780}{3000} \\ = \frac{780}{50} \\ = 15.6 \: minutes$