3 Tips for Adding Quickly
What do speed reading and speedy arithmetic have in common? What’s the fastest way to come up with approximate answers to addition problems? And how can multiplication help you add faster? Keep on reading The Math Dude to find out!
While I was out and about doing some holiday shopping this week, I realized that I somewhat unconsciously use several mental addition tricks to help me keep track of how much money I’m about to spend. After noticing this, I also realized that these tricks probably aren’t the obvious ones that people use all the time – which is why I thought I’d share them with you today.
In particular, we’re going to learn the connection between speed reading and speedy addition, the fastest way to add numbers when you only need an approximate answer, and how multiplication can speed up addition.
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Tip #1: Just Do It (Don’t Say It)
Today’s first tip is simple to say, hard to implement, but extremely effective once you do so. Here’s the trick: Stop subconsciously talking yourself through mental addition problems. That’s it. Although, as I said, following this advice is easier said than done.
Stop subconsciously talking yourself through mental addition problems.
If you’ve ever learned to speed read—or tried to learn, as I have—you’ve no doubt come across the advice that you must stop subvocalizing as you read. I find this incredibly hard to do when reading, although some people seem to be able to do it. While I find it tough to do while reading, I’ve realized that I do it naturally when adding up a list of numbers.
For example, when tallying a list of numbers like 23, 17, 7, 12, and 31, my inner monologue is not something like:
23 plus 17 is equal to…uh…40, then 40 plus 7 is 47, then 47 plus 12 is 59, and finally 59 plus 31 is…um…90,
but is instead something like:
23, 33, 40, 47, 59, 90.
In other words, I don’t subvocalize what I’m doing – I just do it. In this case, I started with the first number, 23, then added the 10 from 17 to get 33, then added the 7 from 17 (noticing that the 3 and 7 add to form a convenient multiple of 10) to get 40, then the following 7 to get 47, then the 12 and 31.
The point is that I did each step without saying what I was doing to myself. Instead, I just did it. Once you get used to doing that—which, admittedly, does take some practice—you’ll find that cutting out the subvocalization gives your mental addition a huge speed boost. And, for me at least, it’s a lot easier to do this with addition than with reading.
Tip #2: Round Off (and Speed Up)
Today’s second tip is for all of those times when you need to add some numbers to come up with a ballpark estimate of the sum. In other words, it’s for all of those times when close enough is good enough.
One secret is to go ahead and start your estimating early on in the game by rounding the numbers you’re adding first.
In moments like this, the secret is to go ahead and start your estimating early on in the game by rounding the numbers you’re adding to whatever digit you want. For example, if you’re adding a bunch of 3-digit numbers—say 123, 421, 369, and 876—but only need an answer to roughly the nearest 10, then you should start by rounding all the numbers you’re adding to the nearest 10. Which means that instead of adding 123, 421, 369, and 876, you should instead add 120, 420, 370, and 880. Clearly, it’s a lot easier to add all of these rounded numbers, since they all have a zero in the ones column—which means the addition will be a lot faster.
What’s the big deal here? Well, a lot of times when people want to know the answer to a problem to the nearest 10, they’ll go through and add up all the numbers, and wait to do the rounding until the very end. But that’s a lot slower – and the answer will be similar using either method (since you round up about as often as you round down.) So, it makes sense to round from the start in these situations and make your life easier, don’t you think?
Tip #3: Multiply First (When You Can)
Today’s last tip is really simple – and really obvious, once you realize you can (and should) do it. The trick I’m talking about is to remember to multiply before you add. What do I mean? Let’s look at an example.
Say you’re adding up the prices of a bunch of books you’re buying. Using our previous tip, you’re going to round everything to the nearest dollar from the beginning. When you do that, you have a list of books that are $7, $14, $8, $7, $11, and $7. One way to go about adding these numbers is to start from the beginning and dutifully march forward.
But that’s not the best way. Instead, notice that three of the books cost $7. – which means you’d be better off first multiplying $7 by 3, for a total of $21, and then adding this sum to the other amounts to get the overall total. Or even better, you could notice that one of the other books costs $14 (which is 2 x $7.) Which means you could start by multiplying $7 by 5, for a total of $35, and then add this total to the two remaining prices to get the final amount. The take away here is that multiplying first can really speed things up.
Finally, the real trick with all three of these tips is to practice. No, I don’t mean writing down a bunch of practice problems and solving them one-by-one (that’d be boring.) I mean taking the opportunity to use these methods whenever you can out in the real world. That’s the only way they’ll become second nature—and that, math fans, is what you’re really after.
Wrap Up
OK, that’s all the math we have time for today.
For more fun with math, please check out my book, The Math Dude’s Quick and Dirty Guide to Algebra. And remember to become a fan of The Math Dude on Facebook, where you’ll find lots of great math posted throughout the week. If you’re on Twitter, please follow me there, too.
Until next time, this is Jason Marshall with The Math Dude’s Quick and Dirty Tips to Make Math Easier. Thanks for reading, math fans!
Addition problem image courtesy of Shutterstock.
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About the Author
Jason Marshall is the author of The Math Dude’s Quick and Dirty Guide to Algebra. He provides clear explanations of math terms and principles, and his simple tricks for solving basic algebra problems will have even the most math-phobic person looking forward to working out whatever math problem comes their way.
