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## Numbers & Operations - The Real & Complex Number Systems 159-175

### Course: Numbers & Operations - The Real & Complex Number Systems 159-175>Unit 2

Lesson 2: Intro to addition with 2-digit numbers

# Adding by making a group of 10

Sal adds 5+68 by breaking the 5 into a 2 and a 3.

## Want to join the conversation?

• im confused about this if you already know that the question is ex: 68 +32 why would you do all that instead of just doing the normal way.
• Yes, i agree. You may find something you missed. I will give you a vote for such a good answer.
• I'm doing a practice on "Add 2-digit numbers by making 10" and on this question says
"25 + 47 is the same as ___ + 50". And I used the hints and it said 3 ones from 25 to 47.
Where did the 3 ones come from?
• The 3 ones come from the 25 and are added to the 47 to make 50.
So 25-3 = 22 and 47+3 = 50.
This makes the new sum 50+22 (or 50+22 as I would prefer) which is a sum that does not require carrying any 1's over (so its an easier sum).
• Jean add 35 and 9 .how can she solve using only equations to model her thinking ? explain
• You can broke it down to this much longer but clearer method. You have 3 tens and 5 ones (30 and 5 = 35), and you need to add it to 9 ones. So you can add first the similar numbers, like 5 and 9 which is in ones place value. Doing that would get you to, 14 ones, or 1 tens and 4 ones (10 and 4 = 14). From that 1 tens and 4 ones, you can apply again the previous method by adding first the tens, because they're similar. 3 tens + 1 tens (30 + 10) would give you 4 tens or 40 ones. Now you can add the remaining ones to the 40 ones (or 4 tens) which is 4 ones, and that would give you 40 tens and 4 ones, or 44 ones, or in number form 44.
• I'm confused with 68+5. It seems much more obvious to just round 68 up to 70 by adding 2 that you borrow from the 5. Then add the remaining 3 to the 70 equaling 73. What am I missing? This seems easier and more logical!
• You can do it both ways, rounding or just use normal equations
• so like 50 PLUS 5 = 55
• Yes, because you have 5, and you add 0, which as a five next to it, it will be 55.
• how do you do Adding by making a group of 10
• We are trying to add numbers by taking away from other numbers to make the process easier.
An example is that 4 + 18 is the same as 2 + 2 + 18
We're essentially breaking numbers to form groups of 10's.
2 + 18 is 20, and when you add the final 2, you get 22 (20 + 2)
20 + 2 is easier than adding 4 + 18 if you scale up to numbers you can't grasp.
• if it is 1,000x10,000 you take the the first digit of each number ad you multiply them so 1x1=1 the you add the the rest of the zeros so 1,000x10,000=10,000,000?
• Yes you are right. Multiplying the non-zeros and counting how many zeros to solve that kind of problem makes it faster.
• Hi, I am having some trouble with Adding by making a group of ten. Would anyone have a suggestion for me? I watched both videos, but I didn't get much out of them.
• Look at the bigger number, how much do you need to add to it to make a ten number (10, 20, 30, 40....)
You can take that amount out of the other number and add it to the bigger number. Now you can add them together more easily because the bigger number is a ten.
For example: 7+26
How much do I need to add to 26 to make 30?
2 6+ 4 = 30 so I need to take 4 away from 7.
7 - 4
= 3
So 30+3=33. It's the same answer as 7+26, but for some people it's easier to make then 10 than add random numbers together.