Sue Ling wishes to sew braid trim 3 inches from the edges of a 72-in. by 108-in. tablecloth. How many yards of trim will she need?

Question

How do you complete this problem.  I know the answer is 9 1/3 yd, but how did the book get this?

Answer 1

Picture the tablecloth. The trim is 3 inches from the edge of the tablecloth all round, so it forms a smaller rectangle inside the tablecloth rectangle. The length and width of the smaller rectangle are 6 inches (3 inches from each side) smaller than the tablecloth's length and width, so they are 66 inches and 102 inches. The perimeter of the smaller rectangle is 2(length+width)=2(66+102)=2*168=336 inches. Divide by 12 to get this into feet: 28, and by 3 to convert to yards: 9 yd 1ft or 9 1/3 yards. Like the book says.