The school hall is 4 times as long as it is wide. if the perimeter is 55m, what is the length? and what is the width?

-- The width of the school is ' W '.  We don't know what that is yet,
but we're going to find out.

-- We're told that the length is 4 times as much.  So the length is ' 4 W '.

-- Perimeter is (2 widths) + (2 lengths).

2 widths = 2 W
2 lengths = 8 W
Perimeter = 10 W

-- We're also told that the perimeter is 55m.  That's just what we need.

10 W = 55 m

Divide each side of this equation by 10:

W = 5.5 m

There's the width !
The length of the hall is 4 times as much.

Length = 4 W = 22 m