Mental Math: Adding
How to add in your head.
A week or so ago, I wrote a story about how math wasn’t taught efficiently. I said that people who are good at math almost all find the same shortcuts and the people who aren’t good at math are the ones doing it like we were taught. As a follow-up, I decided to write some articles detailing some of the tricks I use to do math in my head. This is the first of those showing how to add.
- Making 10s (even when none of the numbers add to 10)
Most people know that when they are adding a bunch of numbers they can combine ones that add to 10 to simplify the process. I play a game where we roll 10-sided dice, so I used that to generate some numbers.
Here we have: 9, 9, 7, 5, 3 & 1.
We can easily combine the 1 and a 9 to get 10 and the 7 and 3 to get another 10. this gives us 20 and leaves us with 9, 5, and 3. Rather than adding those 3 numbers, I split the 3 into 2 + 1, steal a 1, and combine it with the 9. Now we have 30 + 5 + 2 = 37. Besides making 10s, the only math I did was to change 3 to 2+1 and add 5+2. All of that is easy enough to do in your head.
