Main content

## 2nd grade

### Unit 3: Lesson 3

Visually subtract within 100- Subtracting 1s using place value
- Subtracting 10s using place value
- Subtracting two-digit numbers without regrouping
- Subtracting a 1-digit number with regrouping
- Subtract within 100 using place value blocks
- Addition and subtraction with number lines
- Subtract within 100 using a number line

© 2023 Khan AcademyTerms of usePrivacy PolicyCookie Notice

# Subtracting 10s using place value

Sal subtracts 40 from 65 by thinking about place value.

## Want to join the conversation?

- Does place values work with decimals?(7 votes)
- There are decimal based place values.(5 votes)

- When Sal shows the 65 is equivalent to 6 tens + 5 ones, why doesn't he just do 65 = 60 + 5? He has already visually shown 6 tens and 5 ones with the drawing shown throughout the video length. Is the intention just to continue to think in place value?(6 votes)
- does place values work with decimals(5 votes)
- Good question! Yes, place values are used for decimals! Starting from the first digit to the right of the decimal point, and going further to the right, the place values are tenths, hundredths, thousandths, ten-thousandths, hundred-thousandths, millionths, ten-millionths, hundred-millionths, and so on forever. Observe that place values become smaller and smaller fractions as we go farther and farther to the right of the decimal point.

Have a blessed, wonderful day!(5 votes)

- hi what happens if you forget to cross out the base ten?(2 votes)
- You will end up with ten more than the actual answer. Say you do 22 - 5, you'll obtain 27 instead of 17.(2 votes)

- how many videos do you need to wach?(2 votes)
- You don't
*need*to watch videos if you understand the concepts.(2 votes)

- How much is100_(0 votes)
- this is so boring🥱(2 votes)
- what is 1236452+46228436(1 vote)

## Video transcript

- [Voiceover] Right
here, we have 65 blocks. And you can count them if you like. But we can represent
them with the number 65. By writing a six in the tens place, we're literally saying
that we have six tens. And this is a 10, this is
a 10, this is another 10, this is another 10, this is a 10, and this is a 10. We have six groups of
ten and that makes 60. And then we have five ones. Five in that orange color. And then we have five ones. And you see them right here. One, two, three, four, five. Now let's do something inter... Well, actually, let me just
first write that down again. Just to emphasize it. We can write down that 65, 65 is equal to six tens, six tens plus five ones. Plus five ones. Now, let's do something interesting. Let's start with 65, so let me write that down again, so we're gonna start with 65. I'm having trouble changing colors. We're gonna start with 65 and I'm gonna subtract... I'm going to subtract 40. I'm going to subtract 40 from that. What am I really doing here? Well, I'm starting with 65, I'm starting with this, and I'm subtracting
four tens and zero ones. Let's subtract four tens from here. Let's subtract one, two, three, four. I took away four of the tens. How many tens do I have left over? Well, I have left over two tens. This is going to be equal to two tens. And how many ones do I have? Well, I still have five ones. So, I still... I still have five ones. And that makes sense. I had five ones, I took away zero ones, so I'm still going to have five ones. What is this going to be equal to? We can write 65. 65. Minus 40. Minus 40 is... Let me do the... I want to do the ones
in that orange color. Minus 40 is equal to, another way of saying two tens is by putting a two in
the tens place, and a... And then we have five ones. A five in the ones place. Two tens plus five ones, or 25.