Final answer:
To find the width of the rectangle, we use the perimeter formula P = 2l + 2w, where w is the width. Solving the equation 2(3x) + 2x = 40, we find that the width is 5 meters.
Step-by-step explanation:
The question asks us to find the width of a rectangle whose perimeter is 40 metres and whose length is three times its width. We start by letting the width be x meters. Therefore, the length is 3x meters. The formula for the perimeter of a rectangle is P = 2l + 2w, where l is the length and w is the width. Given that the perimeter is 40 meters, we can set up the equation 2(3x) + 2x = 40.
Simplifying this equation gives us:
Therefore, the width of the rectangle is 5 meters.