The Way I Do Math

Dangerous Boys March 13th, 2008 Spontaneity

There is a reason my teacher gave up on me.

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You spent your years growing up making fun of kids who are good at math. But now you’re all grown up, and you’ve left high school and realized that in college and the rest of life, being nerdy, and actually knowing stuff is pretty cool. I guess it doesn’t really help you get chicks.

You may not be the sharpest pencil in the cup, and we don’t have much time, so we’re going to need to teach you Speed Math! Multiplying big weird numbers you didn’t memorize off a chart in third grade can be difficult. Try this.

If the number is one to two off of an easier number to multiply, round the number, multiply it, and subtract it from the total. 13×19 looks pretty daunting, but all you need to do is multiply 13 by 20, and then subtract 13. See, it’s easy- 247.

The same goes for 8′s but you have to subtract double off the back end. So 8×65 is the same as 10×65 minus 65×2. Or in other words 650 minus 130 which is 520. Nerd Power! You can even do it with big number like 190×38. Which is close to 200×38, or in other words 7600 minus 380 or 7220 total. It does kinda take a little practice.

You can even mix it up and use division too, that’s like real Nerd Power. So 25×160 becomes 25×4 times 160 divided by 4 and that makes it 100×40. 4000. And that is really easy. And multiplying 50 by 3226 is as easy as dividing 3226 by 2 and then adding two zero’s to get 161300. It’s like falling off a logarithm. That is a horrible joke. I hate you for making me say that. 12×16 or 11×17. Which is bigger? Well, as long as the dimensions add up to the same number, the closer it gets to a perfect square, or in this case 14×14, the bigger it’s going to be. No math necessary. It’s the same thing for buying cases of yogurt. Eight 16 ounce cans, or 12 twelve-ounce cans? No question for me, I’m getting 12 twelve-ouncers. But I have to stress the sum of the numbers has to be the same for this technique to work. Nerd Power! Yeah!

You can also calculate the differences between two sets of numbers and find out which one is bigger. 12 by 16 plus 12 is 12 by 17. 11 by 17 plus 17 is 12 by 17. So, which one’s bigger? 12×16 but we already knew that. It’s closer to being a square. How much bigger? 5 because 17 minus 12 is 5. And if you ever get confused, just remember to subtract the numbers and the result will be the relative size of the second number. What? You have no idea what I am talking about? Yeah, there’s a reason my teacher gave up on teaching me math. She’d show me how to do it, I’d show her how I did it, and she said heh, as long as you get the right answer, I guess it’s okay.

You can do the same thing with non matching numbers, but the further away you get from each other, the more calculating it requires, and the more you ought to just think about getting out your cellphone or a calculator or asking your friend that saw this video and actually understood it. ‘Cause everybody needs a friend like that. I’m your friend. But wait, there’s more.

You can use both techniques in combination. Which is bigger 8×29 or 15×19 and by how much? First compare them both to 15×29.

15×29=15×19+15×10 which is 15×19+150

15×29=7×29+8×29 which is like 8×30-8 which is 240-8 or 232

So 15×19 is 232-150 or 82 more than 7×29

What? You want me to do it again? Hey, rewind, let’s take it from the top.

Transcribed by: Karla W.

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  • 1/12/12 @ 14:34

    The Perspicacious Loris

    We learned about logarithms yesterday…

  • 1/11/12 @ 5:25


    I learned a cool new math trick. If you need to multiply a number with itself like 42^2, you can just do it like this. 42-25 = 17 , then add two zero's so you get 1700. 50-42 = 8 ... 8^2 = 64 1700 + 64 = 1764 42^2 = 1764. It works every single time. It is not always the easiest solution, like with 32, you still need to square 18, which is not easy to do from the top of your head. ... (more)
  • 5/22/11 @ 10:13

    The Perspicacious Loris

    I think I found the mistake!

  • 4/28/11 @ 12:20


    When Benton saw what I had just posted, he thew his arm into the air and yelled, “Nerd power!”. Ha ha! Brett and Jedd, you guys are the best!

  • 4/28/11 @ 12:18


    My 11 yr. old son, Benton, loves math and does everything in his head. His method of rounding, multiplying, and then subtracting has always frustrated me. (...even though he's right 99% of the time...) After watching this episode, I am humbled. Shame on me for trying to "fix" him! Obviously, the more clever and insightful people in this world, like Benton and the Brothers Winn, don't need scr ... (more)
  • 4/25/11 @ 1:52


    I figured out the trick of multiplying by an easier number and then adding/subtracting when I was five or six. This meant that everyone else in the class was reciting the times tables from memory and I was doing calculations based on the five and ten times tables. My teacher tried to put me in extra maths lessons because I was slower than everyone else... until my mum had a massive go at her becau ... (more)
  • 1/11/11 @ 17:38


    I see the mistake! Just a transfer over kind of mistake but I still see it.

  • 9/3/10 @ 22:30


    *falls down*

  • 9/3/10 @ 22:26


    *spins*im dissy?

  • 11/23/08 @ 20:31


    I totally found the mistake! It was actually really easy to find even before you announced that it was there….

  • 11/6/08 @ 15:45


    I found your mistake!

  • 9/11/08 @ 16:42


    Wow, my brain hurts.

  • 8/1/08 @ 8:16


    Not sure if you read all these comments, but did anyone ever find out what the mistake was? I’m curious to find out what the mistake actually is.

  • 7/25/08 @ 15:35


    Nerds rule, geeks drool…

  • 7/25/08 @ 13:25


    oops i just realized that i wasn’t supposed to post it! my bad…sorry

  • 7/25/08 @ 13:24


    ha i found your mistake!!!!
    you said:
    15×19=232-150 or 82 more than 7×29
    or in other words
    15×19=232-150 or <– incorrect
    15×19=(7×29)+82 <– correct

    285=85….um no not really equal…but nice try.

  • 7/24/08 @ 12:55


    ok i think i found your mistake….but i’m not sure so i’m gonna check with my hubby and figure it out. (We both love math!)

  • 7/18/08 @ 17:35


    lol…OOoohh! Now I know how! I once solved a math problem in jr. high school using some contrived method that was COMPLETELY different from the “correct” way to do it. My teacher asked me what my logic was behind the method (because I got the problem RIGHT) and I couldn’t remember how I did it. *sigh* I think I might have been a genius for a few minutes of my life.

  • 6/29/08 @ 15:36


    =o guess who just found the mistake! nerd power!! =D

  • 6/26/08 @ 7:45


    i actually get it =D nerd power!!

  • 6/22/08 @ 20:21


    you know there’s just a certain point at which you need to say, “i don’t know. thinking about it makes my head hurt.”

  • 5/16/08 @ 5:22


    I do that, too. Nerds make more money, usually. That makes them so cool. Women love men who make lots of money. Ask Bill Gates or Donald Trump. I get weird looks, and no one quite gets it. But, I’m always right.

  • 5/13/08 @ 9:13


    The Mistake is “being nerdy and actually knowing stuff is pretty cool”, that’s the mistake, right? Being Nerdy is NEVER cool, HA! Where’s my prize?

  • 5/3/08 @ 5:05


    I do stuff like this. I always get these weird looks.
    Although honesty forces me to say that I do complicated things on paper.

  • 4/24/08 @ 15:27


    Nerd power! This isn’t that hard to do it…. *cough*

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