Authors: Laura Laing
Tags: #Reference, #Handbooks & Manuals, #Personal & Practical Guides
Math for Grownups (21 page)
1¼ inches
+
18 inches
=
19¼ inches
That means Reggie needs four squares of fabric that measure 19¼ inches on all four sides.
Buying the fabric is the next step. At Yard by Yard, Reggie heads to the decorator fabrics, looking for something sturdy, without a lot of stretch.
Two fabrics catch his eye: a lime-green polka dot on cream, and a fuchsia paisley. The polka-dot fabric is 54" wide, and the paisley is 48" wide. This is where his calculator will come in handy.
How many pillows can Reggie fit along the width of the fabric?
Each pillow is 19¼" wide. He knows he needs to divide the width of the fabric by that number. Instead of trying to convert the ¼" to a decimal, Reggie just rounds down to 19. Dealing with the 54"-wide fabric first, he divides:
54"
/
19"
=
2.8
Now the 48"-wide fabric:
48"
/
19"
=
2.5
Reggie can get only two pieces across each of the fabrics. Which one should he buy? He’ll have less fabric left over with the second one, and besides, he always thought that room could use a punch of pink. Fuchsia it is!
But how many yards? The length of the side of his sketch will help here, too. He needs pieces for two pillows. Because two pieces will fit on the 19" length of 48"-wide fabric, he needs just two 19" lengths (19" • 2 = 38″).
But fabric is sold by the yard, so he still needs to convert again. How many yards is 38"?
There are 36 inches in 1 yard (12 inches in a foot and 3 feet in a yard: 3 • 12 = 36). Reggie needs to divide the number of inches he needs by 36 to find out how many yards he needs.
39 inches
/
36 inches
=
1.09 yards or 1 yard 3 inches
Whether you’re scrapbooking, welding, sewing, or woodworking, you may find yourself dealing with metric units occasionally. This handy chart will help you convert metric units to standard units.
Knowing some basic fraction-to-decimal conversions is really helpful, too.
He needs a little more than 1 yard, but not much. Reggie decides on 1¼ yards.
Now all he needs is a spool of thread, some needles, and a few hours of free time.
Heidi Klum, here he comes!
Fabrics have standard widths that vary by type of fabric. Here’s a typical list of fabric widths, although they may vary from manufacturer to manufacturer.
If you’re lucky enough to score vintage fabrics, you might find some even stranger widths.
By the way, because width is measured in inches, use inches when you convert your measurements. It’s much easier to figure out what you need if you’re already working with like units.
Mary has decided to take up scrapbooking. She’s a terrific photographer, and she’d like to highlight her art in some special ways. Besides, her mother’s birthday is coming up, and she’d cry if she received a scrapbook of photos of Mary’s kids.
Any new hobby requires materials, and scrapbooking is no exception. Mary picks up an album, some acid-free paper, adhesives, and a few nice pens. Then she starts thinking about the types of pages she wants to build.
Mary loves spreadsheets, so she opens one up and starts typing. She read somewhere that a two-page spread shouldn’t have more than 10 photos. She can break this rule if she wants, but it sounds like a good frame of reference.
Mary starts categorizing her photos, and here’s what she ends up with:
Clearly, she’s going to need more pages for some subjects than for others.
There’s something else Mary needs to consider. Her final single-page count must be divisible by 4. That’s so she doesn’t have any blank pages.
Using trial and error, Mary finagles the number of photos and the number of pages until she comes up with this count.
Using her spreadsheet application to total the pages, she finds that she’s planned for 30 pages. But that’s a problem. Thirty is not a multiple of 4. In other words, 4 doesn’t divide evenly into 30.
Mary thinks a moment. What multiple of 4 is closest to 30? Well, 28 and 32 are both close to 30. Should she add 2 pages or subtract 2 pages?
Mary thinks again. Then she picks up her copy of
Moby Dick
from the coffee table. There’s the cover—just like the cover of her album—and the title page, then hundreds of 2-page spreads, and finally the back page.
Mary hadn’t considered the first and last pages!
It makes sense for her to add 2 pages. That way, she can do a nice title page and wrap things up at the end—maybe with a cute picture of grandma and the kids.
She has a plan. Now all Mary needs to do is figure out the differences between glues, adhesive tapes, and photo corners.
A
multiple
is what you get when you multiply two numbers. (What you get is also called a product.)
Any multiple of a number is evenly divisible by that number—which means there won’t be anything left over. So, if you multiply 9 (let’s say) by 3 to get a multiple of 27, you’ll find that the multiple (27) is divisible by that number (9). And there are no pesky fractions left over. That makes sense, because you used 9 to get the product in the first place. Obviously, you can use 9 to divide the product.
Multiplication and division are opposite, but they’re related operations. Let’s look at another example:
4 • 6
=
24
So, 24 is a multiple of 4 and 6, because we multiplied 4 and 6 to get that product.
And according to our rule, that means the multiple (24) is evenly divisible by 4 (the quotient, or answer, is 6) and also is evenly divisible by 6 (in which case the quotient is 4).
But wait! There’s more! A
factor
is a number that divides evenly into another number.
4 • 6
=
24
So 4 and 6 are factors of 24.
Can you think of another factor of 24?
And if you multiply two (or more) factors, you get a multiple. Which is how we started this whole discussion.
If your photos are stored electronically, you can size them easily using software. But before that software existed, book publishers, newspaper designers, and even yearbook editors had to depend on good old proportions to blow up or shrink photos. And in fact, this is exactly how image software works today.
Remember, a proportion is a pair of equal ratios. If you change one of the numerators, you have to change its corresponding denominator in the same way. Otherwise, the ratios will no longer be equal.
Let’s say you have a photograph that is 6 inches tall by 4 inches wide. You’d like to enlarge it so that the width is 6 inches. If you change the width without changing the height, you’ll have an odd-looking photo. So if you change the height proportionally to the change in the width, what will the height of the new photograph be?
First set up the proportion, using the heights as the numerators and the widths as the denominators.
Then cross-multiply and solve for
x
.
