January 2019
Beginner
400 pages
10h 21m
English
Content preview from Algebra II For Dummies, 2nd Edition
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Chapter 18
Ten Multiplication Tricks
IN THIS CHAPTER
Saving time on tests and homework problems with fast multiplication
Avoiding calculators and division (and sometimes multiplication itself)
You studied your multiplication tables way back in the third grade. You can quickly rattle off the product of 7 and 9 or 8 and 6 (can’t you?). In this chapter, you discover some new patterns and tricks to help you with products and processes — tricks that save you time. You’re also more apt to get the right answer when using these tricks (not that you ever have the wrong answer, of course). And think of how you can amaze your friends and colleagues by pulling seemingly tough answers out of thin air.
But before you get moving, I have a confession to make: I’ve snuck in an addition trick as well because I know that you’ll love it.
Squaring Numbers That End in 5
You know that 5 squared is 25. But what about 
, and so on? Don’t have your calculator on you? No worries. To square a number that ends in 5, follow these steps:
Write down the last digits of the answer: 25.
The squared form of a number that ends in 5 always ends with 25.
- Take the digit or digits in front of the original 5 and multiply ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.