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@LukeAlmighty > Say you want to add two-digit numbers. The old-school way millennial parents were taught involved putting one on top of the other and carrying, if necessary. Now, students are encouraged to rethink how they arrange the numbers. Moldavan gives the example of 41 + 29. You could rewrite 29 as 30, which is a rounder, "friendly number." Then, you turn 41 into 40 (also "friendly"). You've subtracted 1 from 41, and added 1 to 29, so that cancels out. And now you have your product: 70.

> Another strategy is called "making 10s." "Say you want to add 8 + 6 + 2," says Moldavan. "You might rearrange the numbers so you can quickly make a 10. So, you'll add 8 + 2, and then add 6 to get 16."

https://www.parents.com/kids/education/math-and-science/new-math-method-explained-for-millennial-parents/

This is what I've always done in my head. What is wrong with it?