The Power of Forgetting (28 page)

Coming up with this shortcut represented a pivotal time in my life. I was in the sixth grade at a junior high school where Arnie Benson, the eighth-grade math teacher, had a reputation for an unusually fast mind and an extraordinary ability to work with numbers. The first person I met who was really good with numbers (outside of my dad and his brothers), Arnie was someone I looked up to and would target as the person to surpass. When word got around that I might be able to beat him in a game of multiplying single-digit numbers with two-digit numbers, a competition was called. And I beat him. When the competition was over, Arnie said to me, “Mike, next time we’re doing it all with
two-digit
numbers.” He didn’t realize that I had no mental shortcut for performing two-digit-by-two-digit multiplication. I could multiply single-digit numbers by two-digit numbers in my head all day long, but double digits by double digits? I had no idea how I’d pull that one off, so I sat down and vowed to figure
out a simple shortcut that would work well enough for me to beat him again.

Luckily, we never met in competition again. But I did work out a formula for performing this kind of math in my head that set the stage for me to come up with other formulas and shortcuts. Once I realized that there was more than one way to solve problems, I knew that this principle could be applied to just about any problem in life. I no longer had to rely solely on the rules and steps that were given or taught to me. I could navigate through numbers, words, and other patterns however I wanted, paving a different path and arriving at an equally accurate answer.

Arnie is enjoying his life today in Dallas, Texas, and is as sharp as ever. We still keep in touch, for his influence on me and my time in his classroom were the defining moment in my life when the door opened wide for me to begin creating all sorts of shortcuts to stay ahead of everyone else. Arnie kept me on my toes; I never wanted to run into someone again who’d challenge me to a game that I couldn’t win! To this day, the mere thought of being tested or outsmarted inspires me to keep thinking up new pathways to solutions and ever more shortcuts to successful outcomes.

Even if you hate numbers and math, I challenge you to attempt this exercise. I promise you that once you get the hang of it, you’ll want to do it over and over again and show off this secret maneuver to your friends.

First let me take you through the steps of performing this calculation, and then I’ll give you a few equations to try yourself. If you need to use a pen and paper the first time or two, go ahead. But at some point I want you to rely solely on your mental skills so your mind gets used to jumping
through these hoops—picking up and dropping off information. This shortcut works like a charm every single time you want to multiply a two-digit number by a two-digit number; it’s one of my own original inventions. At first it may seem long and tedious, especially when you try doing it all in your head, but once you have the steps down and have practiced them, it will become automatic.

Reminder: In the following exercise I will use language like “tens digit number” and “ones digit number” as I explain the steps. This helps me to identify which numbers to use. You should already be very familiar with this language from previous chapters, but here’s a cheat sheet again just in case:

In the number 23, the 3 is called the ones digit number; the 2 is referred to as the tens digit number.

Here’s the first equation:

Step 1:
Multiply the tens digits together: 3 × 5 =
15
.
Hold that number in your head
.

Step 2:
The second and third steps are the hardest. First, cross-multiply the numbers: 5 × 2 = 10 and 3 × 1 = 3, then add 10 + 3:
13
.

You’ll need to keep this number, 13, in your head. You will use this number to make an adjustment to the first number, 15, which should still be in your head. If it helps, you can think of the number 13 here as just a 1 and a 3.

Step 3:
Now add the tens digit number of the new number, 13, which is 1, to the first number in your head (15 + 1 = 16), then tack on the 3 to get 163. This is the new number you’ll need to remember. Drop all previous numbers from your head and keep only
163
.

Step 4:
Finally, multiply the ones digits in the original equation (1 × 2 = 2) and tack the product onto the end of 163. And now you have your answer:
1,632
.

Confused? Bewildered? Lost? Let’s do this exercise again with a new set of numbers. Once more, if you need to use a pen and paper to drill down each step and create a mental image of the process, feel free to do so. Okay, let’s try the following:

Step 1:
Multiply the tens digits (6 × 4 = 24). Keep the number
24
in your head.

Step 2:
Cross-multiply (6 × 5 = 30; 2 × 4 = 8) and add (30 + 8) to get
38
.

Step 3:
Recall that you had the number 24 in your head from the first step. Now you’re going to use this new number, 38, to modify the first number. Take the 3 and add it to 24, which gives you 27. Then tack on the number 8, and you arrive at
278
.
Keep this new number in your head and ditch the previous one
. Say it a few times: two-seven-eight, two-seven-eight. Then it’s in your head and it will stay there.

Step 4:
Go back to the original equation (62 × 45) and multiply the ones digits (2 × 5 = 10). Uh-oh, the last time we did this exercise we didn’t get a two-digit answer. So what do we do here? We cannot just tack on a 10 to the end of 278. What we have to do is one more little step, similar to what we did before. We add the tens digit of our number, 10, which in this case is the number 1, to 278, and we get 279.
Then
we can tack on the ones digit number, 0. Now you have your answer:
2,790
.

Did you follow that? Are you still feeling queasy? Don’t panic if you’re not totally in sync with me yet. That’s normal, as this trick can take time to get down, much less commit to heart. If you don’t feel fully confident enough in the methodology to proceed, go back to the beginning of this section and review every step for both examples using all of your focus and concentration. Make sure you don’t have any distractions keeping you from absorbing this systematic process. When you’re ready, it’s time to try this calculation on your own and
in your head
.

Below are two more sets of equations. See if you can do this without pen and paper (or a calculator!). Work at your own pace as you master this shortcut. Don’t worry if you struggle the first few times you do this exercise. You’ll find the solutions to these equations at the end of the chapter. For a video demonstration of multiplying two-digit numbers, go to
www.MikeByster.com
.

Tip:
As you work through these problems, really focus on the forgetting part. Be mindful of the numbers you have to keep in your brain at every step, and when you reach a crucial intersection where you need to mentally drop a number and pick up a new one, see if you can be acutely aware and hyperconscious of that exchange. The “drop off and pick up” juncture is a place of vulnerability. If you’re not paying attention, you can lose track, make an unintentional fatal mistake, and end up with the wrong answer. It’s like you’re working on an assembly line that processes different numbers. As one number comes your way, you speedily tend to it and then you have to let it go as it moves on past so you can handle the next number coming down the line. If you take too long tending to a certain number, the whole assembly line can get backed up—or break down and stop entirely. Keep it going by staying focused on the task at hand. Maintain a steady cycle of “find and forget” in your head until you have your answer.

Self-Test 1

Self-Test 2

Now let’s turn to the next exercise, which will help you improve another aspect of the forgetting skill: evaluating information and immediately dumping the superfluous or no longer relevant. Again, this lesson employs numbers, but training your brain using an activity like this will help you “forget” automatically when it comes to other subjects, including everyday tasks like instantly picking out the highlights from a lengthy article or fishing out the bottom-line message in people’s presentations or in crucial conversations you’re having. This particular exercise puts your listening skills to the test, so pay attention!

THE SECRET NUMBER

This game requires at least two people and works best in groups of three or more. Here’s how it works: One person picks a number between 100 and 1,000. The other players have to guess what that number is while the person with the secret number says “higher” or “lower,” depending on their guesses. The person who states the correct number after the fewest guesses wins.

How does this game help sharpen your forgetting skills? Well, during every round of calling out numbers and narrowing down the range, a new range of numbers is considered
while all other numbers outside that range are thrown out. So, for example, if your secret number is 437 and someone guesses 500, you’ll say “lower”; if the next guess is 300, you’ll say “higher.” Now the range of numbers is between 300 and 500. Future guesses will constantly shift this range. This forces players to continuously keep only a certain defined series of numbers in their heads at any given time and to forget about the rest. If you try to keep all the numbers in your head, you’ll quickly lose focus and won’t be able to stay on track. Ditching and forgetting the disqualified numbers is key to staying in this fast-paced game and to winning. The game’s added bonus is that it also enhances everyone’s listening skills. Often the person who wins this game isn’t the person with the fastest mind—it’s the one who can totally focus on the “active” numbers, concentrate on the direction the person with the secret number gives (“higher” or “lower”), and stay on top of the moving flow of changing numbers. All of these skills require forgetting, but they also demand an intense level of listening.

You can also build in other rules to make this more difficult. You could, for instance, eliminate or penalize people who go the wrong way when they are told “higher” or “lower.” If you’re playing with just yourself and one other person, the goal is to become faster and faster at arriving at the secret number with the fewest guesses (and outpace the other person when it’s their turn to try guessing the secret number).

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