- Add and subtract within 100: FAQ
- Adding 2-digit numbers without regrouping
- Understanding place value when adding ones
- Understanding place value when adding tens
- Adding with regrouping
- Add within 100 using place value blocks
- Addition and subtraction with number lines
- Add within 100 using a number line
Understanding place value when adding ones
Sal adds 37 + 2 by thinking about place value.
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- At1:24, Sal mentions tens and ones instead of the 37. What does he mean?(1 vote)
- He means that after adding 37+2,how many tens and ones are there going to be?
It is going to be 3 tens and 9 ones.
Hope that helps! :)(3 votes)
- So, this right over here is one way to represent the number 37. The number 37 has a three right over here in the tens place. So, this three literally represents three tens. Notice, this is a ten here, this is a ten here, and this is a ten here, three tens or 30. You see each of these tens, there's one, two, three, four, five, six, seven, eight, nine, ten. Now, the seven is in the ones place. It literally represents seven ones. You see that right over here, one, two, three, four, five, six, seven, so you can say that 37 is equal to three tens, do this in the purple color, is equal to three tens plus seven ones. Now, what if I wanted to add something to 37? What would 37 plus two be equal to? How many tens and how many ones? Well, let's think about it. We're now going to add two, so we're adding two ones, so we're going to add one and two. So, now we still have three tens, so let's write that down. So we still have three tens, but now we have a different number of ones, we now have one, two, three, four, five, six, seven, eight, nine, we now have nine ones. Another way to think about it is seven ones plus two ones is nine ones. So let me write that down. So, plus nine ones, or another way to think about it is 37, let me just write it the same way, 37 plus 2 is equal to three tens, so I can write this as 30 and then nine ones, is equal to 39, and that's exactly what we have here. We have 30, this was the three tens, and then we have nine ones, which is 39 squares.