Question

Find the perimeter of a rectangular field whose length is 4times its width and which has area equal to 20736 sq. m

Answer 1

l=4b
area =lb=4b^2
4b^2=20736
b^2=20736÷4=5184
b=72
l=288
perimeter=2 (288+72)=360×2=720m

Answer 2

let bredth be x

area=L×b
20736=4x×x
20736=4x²
4x=√20736
4x=144
x=36
now x=36,
so length=144m

perimeter=2(l+b)
=2(36+144)
= 360