Question

a carpet is laid on the floor of a room 8m by 5m.there is a border of constant width all around the carpet.if the area of the border is 12M^2 find its width

Answer 1

Let width of carpet be 'x'm
Therefore, inclusive of border:
Length of room = 8m
Breadth of room = 5m
Length of carpet = 8-x-x = (8-2x)m
Breadth of carpet = 5-x-x = (5-2x)m

Area of room (carpet + border) 
=  8*5 = 40sq.m

Area of just carpet
= (8-2x)(5-2x)
= (40-16x-10x+4x^2)
= (4x^2-26x+40)sq.m

Area of just border = 12sq.m (given)

Therefore,
Area of ground = Area of just border + Area of just carpet
=> 40 = 12+(4x^2-26x+40)
=> 0 = 4x^2-26x+12
=> 0 = 2x^2-13x+6 (dividing equation by 2)
=> 0 = 2x^2-12x-x+6
=> 0 = 2x(x-6)-1(x-6)
=> 0 = (2x-1)(x-6)
=> x = 1/2 = 0.5m or 6m

discarding 6m since it is longer than room then

Therefore, width of border = 0.5m

Answer 2

The width of the carpet is 50 cm.