What is the length of a rectangle whose perimeter is 64cm if the length is 3 times the width?

Let's denote the width of the rectangle as ( w ) and the length as ( 3w ). The perimeter of a rectangle is given by the formula ( P = 2l + 2w ), where ( l ) is the length and ( w ) is the width. Given that the perimeter is 64 cm, we can write the equation ( 64 = 2(3w) + 2w ). Solving this equation, we find that the width is 8 cm and the length is 24 cm.