3rd grade foundations (Eureka Math/EngageNY)
- Hundreds, tens, and ones
- Write numbers in different forms
- Comparing whole numbers
- Compare 3-digit numbers
- Subtracting 2-digit numbers without regrouping 1
- Subtracting two-digit numbers without regrouping
- Subtract within 100 using a number line
- Subtracting a 1-digit number with regrouping
- Subtract 1-digit numbers with regrouping
Sal subtracts 31 from 64 by thinking about tens and ones.
Want to join the conversation?
- I honestly don't get it. Why use the ''tens'' and the ''ones'' why not just do
- Do it either way, whatever works best for you. They do it that way to help explain it better, but if you already understand do whatever you want. If you have to do it like that as part of the lesson, it isn't very hard so you should be able to get through it quickly. Nice name, BTW(17 votes)
- I would like you to pause the video and think about what 64 minus 31 is. Alright, now let's think about this together. So what does 64 actually mean? Well we can use place value to think about that. The six is in the tens place and the four is in the ones place. So the six over here, that means six tens. It means six groups of ten. And so, we can visualize that right over here. Six tens, one, two, three, four, five, six groups of ten. Or another way to think about it, six tens, these are 60 boxes right over here in groups of ten. And then we have four ones. Well this is four ones right over here. Four ones. So this is 64. Six tens, four ones. Altogether I have 64 boxes. Sixty of these blue ones and I have four ones. Four of these individual ones. Now I want to take away 31. Well what is 31? Thirty-one is three tens and one one. So let's first take away the one one. We're going to take this away, we're subtracting. We're subtracting three tens and we're subtracting one one. So let's take away that one one. And then how many ones are we left with? Well now we're left with three ones. So four ones minus one one is three ones. Now let's think about the tens. So I had six tens. I'm going to take away three of them. I'm going to take away three of the tens. So let's do that. Let's take away, that's one ten, two tens and then three tens. And so what am I going to have left over? Well I'm going to have left over, just three tens. Just these three, these three right over here. So six tens minus three tens is three tens. And so 64 minus 31 is 33. Three tens and three ones. Three tens, this is a group of ten, another group of ten, another group of ten. Three tens and then three ones. One, two, three.