If 42cm is the diameter of the circle, the circumference of the circle is 42π, which we can simplify later. 42π multiplied by 60% (which is equal to 0.6) is 25.2π, which is the perimeter of the rectangle. Let x be the width of the rectangle, which will make the length of the rectangle 3x since the length is 3 times the width. The formula for the perimeter of a rectangle is 2(l+w), where length (l) is 3x and width (w) is x which will make the perimeter  2(3x+x) which is equal to 8x. Also, 25.2π is the perimeter of the rectangle. So, the equation is 25.2π = 8x. Multiply both sides by 1/8, will result to x = 3.15π which is the width of the rectangle. Multiply 3.15 by π (where π = 22/7), will result to 9.9. Therefore, the width of the rectangle is 9.9cm.
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