Question

the length of a rectangular floor is 20m more than its breadth if the perimeter of the floor is 280m what is its length

Answer 1

given,
l=b+20 ..................(1)
2(l+b)=280
then,
2(b+20+b)=280
2( 2b + 20 ) = 280
2b+20 = 140
2 (b+10) = 140
b+10 = 70
b=60
from (1)
l=b+20
l= 60+20
l= 80

Answer 2

let breadth=x.
length=x+20
perimeter of a rectangle=2(l+b).
=2(x+x+20)=280
=2(2x+20)=280
=4x+40=280
4x=240
x=240÷4
x=60
therefore b=60
l=b+20
l=60+20
l=80