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2nd grade
Course: 2nd grade > Unit 3
Lesson 1: Visually adding within 100- 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
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Adding 2-digit numbers without regrouping
Sal adds 23 + 45 thinking about place value.
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What if you group the numbers before addition(18 votes)
It would be the same concept except backwards, you would still get the same answers. 800+50+3=853 358=300+50+8(6 votes)
Even though I just started this, I wonder how to do proportions? Not the x over 4 or anything. I mean like, 4:5 or something. So hard tbh. Or maybe i'm just slow. Please help. Thanks!(8 votes)
I think you just break the work into parts and do it one by one sp that you do not get stressed or angry.👍(9 votes)
Can we count by 2s to 100(6 votes)
Yes. You would go by 2 50 times, because 2 x 50 = 100.(3 votes)
why is subtraction a thing(1 vote)
I guess if you think about it it's because addition is a thing. Adding is putting groups together, so something needs to describe separating groups. We call this subtraction.(13 votes)
Why is regrouping important? Why Ithink it is important is because for example you cant subtract 32 from 56. So you have to regroup riight?(5 votes)
In an addition problem, you need to regroup if there are more than 10 ones or 10 tens. In a subtraction problem, you need to regroup if there are not enough ones or tens to subtract.(3 votes)
- can we use another kind thing to help us with math?(5 votes)
- What kind of thing will you want us to use to help you in maths?(1 vote)
Do you regroup the numbers?(4 votes)- We group numbers to make them easier to work with. Because we use a base-10 number system, we group numbers in multiples of 10. Ten 1s are the same as one group of 10. One hundred 1s are the same as one group of 100. Most of the time, one group of 10 or one group of 100 is easier to work with than ten 1s or one hundred 1s.(3 votes)
- Your adding the tens and ones.(4 votes)
- Is there a different way to do this?(3 votes)
well, yes. but were doing this way.(1 vote)
Can you regroup any number?(3 votes)
You can regroup any number greater than 10. For example: 84 is 8 tens and 4 ones.(2 votes)
Video transcript
So above this dotted line, I have a certain number of boxes. And we could see each of these gold bars, they have 10 boxes in them. 1, 2, 3... 4, 5, 6, 7, 8, 9, 10 And I have two groups of these tens. So I have two tens. I have two tens and I have 1, 2, 3 ones. That's how many boxes I have above that line and below that line... I have 1, 2, 3, 4 tens. Four tens. And I have 1,2,3,4,5... I have five ones. So, this first number is two tens and three ones or 23. Two tens, three ones. The second number is four tens and five ones. Four tens and five ones...45, now, what I want to do is add the numbers. So let's do that. So let's add, so let's add that amount. This amount to this amount. 23 to 45. Well, I have three ones here, I have five ones here, so if you add those to those you're going to end up with eight ones. So let me do that in that blue color. So you're gonna have: 1, 2, 3, 4, ... 5, 6, 7, 8 and if we look at it... look at it over here where we write down the numbers with digits, or with numerals. Then here you're gonna have three ones plus five ones is eight ones. Eight ones... eight ones. Now you have two tens plus four tens. Well, that's going to be six tens. So let me actually copy and paste this. So I have two tens. So two plus four is six. So two, four and... two, four and six. So I have... I have. Let me change my tools. So I have 1, 2, 3, 4, 5, 6 tens Woops, using the wrong thing. I have... I have six tens. So just like that, you can see when I had 23 to 45, I just added the ones place. Three plus five was eight. Three plus five is eight. Three ones plus five ones is eight ones. And I added the tens place. Two tens plus four tens is equal to 6 tens. So I got 68.