Subtraction within 100
Subtracting 2-digit numbers without regrouping 1
- [Voiceover] Let's try now to subtract some two-digit numbers. Over here, we have 65 minus 23, and I encourage you to pause the video and see if you could figure this out. I'm assuming you've had a try at it. Let's do it together. The way I like to do it is I start in the ones place, and the numbers in the ones place I've colored them in in yellow, so this right over here is the ones place. This over here in purple is the tens place. I could even do a column here, where everything in yellow, this is the ones column. I guess you could think of it that way, everything there is in the ones place. They're representing a certain number of ones, and then everything in the second column, everything in the second column is in the tens place. They represent a certain number, a certain number of tens. 65 is six 10s and five ones. 23 is two 10s and three ones. One way to do it is, say, let's look at the ones place first. I'm taking three ones away from five ones. Five ones minus three ones is two ones. Then, you can go to the tens place. Six 10s minus two 10s, well, that's going to be four 10s, four 10s, and there you have it. This is equal to 42, and once again, I could have written it multiple ways. I could have written it like this. I could have written 65 as 6 tens, six tens, + 5 ones, plus 5 ones. I didn't write over here because when I have something in this place, that means it's tens, but here I can write it out, 6 tens. If I'm subtracting 23, that's the same thing as subtracting two 10s, subtracting 2 tens, and then subtracting three ones, and then subtracting 3 ones, subtracting 3 ones. What's that going to be? Well, 5 ones - 3 ones is exactly what we have over here. It's going to be 2 ones, and 6 tens - 2 tens, well, that's just going to be 4 tens, 4 tens. 6 tens + 5 ones - 2 tens - 3 ones is going to be 4 tens and 2 ones, four 10s and two ones, or 42. 42 is equal to 4 tens + 2 ones. Hopefully, that makes a little bit of sense.