There is a reason my teacher gave up on me.
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?
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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