Inactive Tutor answered 12/02/20
First, express the side lengths of the field as algebraic expressions. The length is an unknown variable, and the width is six meters less than that variable.
L = x
W = x - 6
Now, we know the value of the perimeter when each of these values is doubled is 120 meters. So, first we need to double the side lengths.
2L = 2x
2W = 2(x - 6) = 2x - 12
Now we write an expression that will tell us the perimeter of this hypothetical field with the doubled side lengths. You probably know that a perimeter is twice the width plus twice the length, so the width of this doubled field will be:
P = 2(2x) + 2(2x - 12) = 4x + 4x - 24 = 8x - 24
We know the perimeter of this doubled field is 120 meters, so now we know:
120 = 8x -24
Now solve the equation.
144 = 8x
x = 18
Now we know that the length of the original field is 18 meters. The width is 6 meters less than the length, so we know the width is 12 meters.