Save more with math

math-for-grownupsThis guest post is by our friend Laura Laing, a Baltimore author of the new book “Math for Grownups.” You can read more from Laura at her blog, Math for Grownups.

She’ll be talking about the book at 6:30 p.m. Sept. 20 at The Ivy Bookshop, 6080 Falls Road, in Baltimore.

You can get the e-book free through today, Sept. 10.

Saving some bucks can be a thrill and also a big boost to the bottom line. But did you know that a little bit of math can help you save even more? Take a look:

For the Day or the Year?

Your four kids have been clamoring to see the baby seals at the National Aquarium in Baltimore all summer long. But dang! Those tickets are pricey! You spot an online deal: 10% off each child’s ticket. Can you do better?

Here’s where looking at an annual membership might be a better deal. Let’s look at the numbers. If an adult ticket is $24.95 and a kid’s ticket is normally $19.95, you’d pay $24.95 + $24.95 + $19.95 + $19.95 + $19.95 + $19.95 or a total of $127.70 normally for two adults and four children. With the discount, each child’s ticket will be $19.95 minus $1.99 or $17.96. That brings your total down to $121.74. But if your family plans to visit twice this year, you can buy a family membership for $159 and save cash without the reduced ticket price.

On the other hand, if you want to visit the National Aquarium in D.C., admission is only $9.95 for people 11 and older and $4.95 for kids 3 through 10, so you’d have to visit four times to make the annual family pass at $159 the better deal – or plan to visit Baltimore and D.C.’s aquariums, which are both covered by the annual membership.

Fly Me to the Moon—with My Luggage, Please

You found a great deal on plane tickets online, but is the best deal? To find out, check the additional fees.

Most airlines today are charging for each bag of checked luggage. So, if your discounted ticket costs $250, but you need to check two bags (at $20 to $25 each), you could be paying up to $300 for the ticket, not including airport taxes and security fees. Another airline, without checked bag fees, could cost you less in the long run.

BOGO May Be a No-Go

By one, get one (BOGO) is always a good deal, right? Not so fast. You’ve found an online coupon for orange juice. If you buy a 64-ounce container, you can get a second one at half the price. Take a look at the other options when you get the store – before you buy.

At your local supermarket, you notice that the BOGO orange juice is $3.48. But there’s another brand on sale for $5.53 per 128-ounce container. First off, the second brand is twice as large as the first. So, whether you use your coupon or not, you’re getting the same amount of juice. But how much would you pay, if you use the coupon? Half of $3.48 is $1.74. (Use a calculator, if you want!) And $3.48 + $1.74 is $5.22. Turns out, BOGO is the better deal.

You may not want to do any math, but if you’re looking for the best deal, a few calculations — and some creative thinking and common sense — can mean the difference between saving and spending.