Jan 23, 2012

Addition L2

Alright, HT here again.
Now we're going to be looking at larger addition problems. 3, 4.... even 5-digit additions.

The principle is exactly the same as 2-digit addition, except you have a few extra numbers to keep track of.
So, enough talk, let's get to an example;
115+435... simple enough... let's break it down into 3 single-digit problems. 100+100, 10+30 and 5+5..
We know that 5+5= 10, so let's add another one to the 30, making it 10+40, which equals 50.. now you've got just one problem left.. 100+100.. easy, right? The answer, then, is 250.

4-digit addition? no sweat.
4613+9846... break it down into single-digit additions; 4000+9000, 600+800, 10+40, 3+6.
which gives the answers, 13000, 1400, 50 and 9. Add them together to get 14,459.

And in case you didn't know, it's easier to add from right to left. Yep, you heard me, right to left. Add the 1's first. Then, if you get an answer of 10 or more, add 10 to the 10's place, and remove it from your initial answer. Need an example?

45+36... 5+6 equals 11.. so add 10 to the 10's place.. which gives 50+30, or 40+40... leave the 1 as the initial answer.. then add the 50+30.. which is 80. Add the two answers, 80+1 to get 81.

Your turn!
Try these problems;

Remember, break them down into single-digit additions, and then add the answers.

HT Fact:
The Handsome Toddler encourages you to look for math problems to do.

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