Adding four two digit numbers

What I want to do in this video is try to figure out what 35 plus 22 plus 10 plus 16 is equal to. So, pause this video and see if you can figure that out.

All right, now let's work through this together. Now, as you will learn, there's many ways to approach this. But the way I'll think about it is by thinking about place value. For example, when we look at 35, we have three tens and five ones. Three tens right over here, that's the same thing as thirty. So you could view thirty-five as thirty plus five.

And we could do the same thing for twenty-two. Twenty-two is two tenths, which is 20—that's what that 2 tells us—plus 2 ones, so 20 plus 2. And then we have 10, which is just 1 ten and no ones, so plus 10. And then 16, we could rewrite that as being the same thing as 1 ten, so 10 plus 6 ones, plus 6 ones.

Now, why was this useful? Now I could take all of the things that are a certain number of tens—so 30, 20, 10, and 10—and try to add those together. And then separately, I will try to add the five, the two, and the six. And when you see when I do it, I think it'll make a little bit sense why it's useful.

So we have a 30 plus 20 plus 10 plus 10 plus that purple 10 plus that purple 10. So I've already accounted for the 30, the 20, that 10, and that 10. And then I'll have all of the things that were written in the ones place before, so plus five ones—so I got that taken care of—plus two ones, that's taken care of—plus six ones, plus six ones.

And now all of these we can think about. What is 30 plus 20? Well, 30 plus 20 is going to be 50. And then 50 plus 10 is 60. And then 60 plus 10 is 70. So that's all going to be 70.

Another way to think about it is we have 3 tens plus 2 tens plus 1 ten plus 1 ten. 3 plus 2 plus 1 plus 1 is seven. So we have seven tens. And you actually saw that up here as well: three tens plus two tens plus one ten plus one ten—that's going to give us seven tens.

And then we can add this other part where we see five plus two is seven, plus six is thirteen. So it's seventy plus thirteen. Now, what is seventy plus 13? Well, I could rewrite 13. I could do something similar as 10 plus 3, and that makes it a little bit more obvious. We can see that that's the same thing as 70 plus 10, which is 80, plus 3, which is the same thing as 8 tens and 3 ones, which is equal to 83, and we're done.