Math for Grownups (20 page)

Aha! Her finished scarf will be 44 inches long.

Now that the math is out of the way, Ann can get to work.

It’s all Heidi Klum’s fault.

Reggie had never been interested in sewing, much less fashion, until Klum brought burgeoning fashion designers to the small screen. He eagerly awaited new seasons—and new episodes—of the fashion design contest. And soon, he was dragging his mother’s Singer sewing machine up from the basement.

He carefully oiled its parts and collected tools from local yard sales—a good pair of shears, a quilter’s rule, a tape measure, and even a jar full of old buttons.

But what is Reggie—a newcomer to the art of fabric—going to sew first? His glance lands on the ratty sofa pillows he’s had for years. Sure, they were pretty when he first bought them, but now, not so much. Plus they’re square, which makes for easy lines and measurements.

Pillow covers it is.

First, he needs to know how much fabric he’ll need. Reggie hunts for his new tape measure. The pillows are indeed square, measuring 1½' by 1½'. He pulls out a piece of paper and sketches a simple square. Then he labels his drawing.

Easy enough. For each pillow, he needs two pieces of fabric measuring 1½' by 1½'—one piece for the back and one piece for the front. Because he is making two pillows, he’ll need four pieces all together.

But then Reggie remembers seam allowances. If he’s going to sew the fabric together, he needs to make room for the seams. But how much room? On a website for beginning sewers, he learns that seam allowances are typically
. He looks again at his sketch, thinking about where the seams will go.

Reggie knows there are four seams in each of his pillows—one for each side—so he needs to add
to each side of the square. Doing some calculations, this is what he comes up with:

Front and back pieces of each pillow =
+ 1½' +

Ugh. Reggie notices two things right away: Not only is he dealing with mixed numbers
and
fractions, but he’s also got two different units of measurement: inches and feet. He’s going to have to do some conversions. He decides on inches.

(Wait! You say there’s an easier way to do this? Yes, you can simply multiply 1.5 by 12. You’ll get the same answer. But know this: Fractions are huge in sewing. Getting some practice with them is not a bad idea if you have sewing aspirations yourself.)

Reggie revisits his addition problem, this time using 18" in place of 1½'. And now that everything is in the same unit of measurement, he doesn’t need to include those annoying little unit marks.

5/8;
+
18
+
5/8;

Clearly, Reggie still has work to do. He can get a common denominator for all of the fractions. Or he can try a different process, to make things easier on himself.

Reggie had the problem arranged this way because he was picturing his pillow: seam allowance + size of pillow + seam allowance. But this is addition, so he doesn’t
have
to add in that order. It makes more sense for him to add the fractions together first and then see what he can do.

Now he’s faced with another choice. 10/8 is an improper fraction—in other words, it’s larger than 1. Should he change it to a mixed number—a whole number and a fraction? He decides to do so. That’s because it’s pretty straightforward to add a mixed number to a whole number.

To change an improper fraction to a mixed number, just divide the numerator by the denominator. The answer is your whole number, and the remainder is the numerator of the fraction part. The denominator stays the same.

He scribbles these steps in the margin.

But wait. There’s something up with Reggie’s answer. The fraction of the mixed number isn’t in its simplest form. That’s not necessarily a huge deal, but this fraction is easy to reduce. All he needs to do is find a common factor for both the numerator and the denominator and then divide each by that number. The 1 just comes along for the ride.

Thus Reggie’s seam allowances add up to 1¼". He can finish the problem now: