About this video
The video solves a word problem: there are 461 homes, and 352 are apartments, so how many are not apartments? It works out 461 - 352 by taking away 300, then 50, then 2 to get 109. Then it shows a second way: subtract 2 from both numbers to get 459 - 350, which gives the same answer.
You'll be able to
- tell when a word problem asks me to take away.
- subtract by breaking a number into hundreds, tens and ones.
- change both numbers by the same amount to make subtraction easier.
Key words
- difference
- The answer when you subtract one number from another.
- place value
- What a digit is worth because of where it is, like hundreds, tens or ones.
- apartment
- A home that is one part of a bigger building.
Transcript
- [Instructor] There are 461 homes in the part of town where Samir lives. He counted that 352 of those homes are apartments. How many of the homes are not apartments? So like always, pause this video and see if you can work through it on your own. All right, now let's do this together.
So we're starting with 461 homes. So we have 461, and we wanna know how many are not apartments. So what we wanna do is take out the number that are apartments. And they tell us that 352 of those homes are apartments. So we'll take out the number that are apartments and what we will left it with is going to be the number that are not apartments.
So we really just have to evaluate 461 minus 352. And as we've talked about in other videos there's many techniques for doing this. We could break apart 352 into the various place values. So we could say that this is the same thing as 461 minus, we'll do this in different colors, minus three hundreds, or 300, minus five tens, or 50, and then minus two, and then minus two right over there.
And then you might be able to figure out that 461 minus 300, that that is going to be, I'm just taking three 100s from this, so that's going to be 161. And then if I subtract 50 from that, well, what's 61 minus 50? Well, that would be 11. So 161 minus 50 would be 111.
Or another way of thinking about it is if you take these five 10s away from these six 10s, you'll be left with one 10, so that would be 100, one 10, and one one. So you have 111. And then you want to subtract that two, last but not least, and 11 minus two would be nine.
So 111 minus two would be equal to 109. But I mentioned there's many other ways that you might try to approach something like this. You could say, hey, well maybe it's easier to subtract 50, or 350 I should say, then 352 and so you could subtract two from both of these numbers.
So if you subtract two from 461, if you subtract one you get to 460, you subtract two you get to 459. 459 minus, you subtract two from this you get to 350. And this is all about the idea that the difference doesn't change as long as you add or subtract the same number to both.
And so here we might say that four 100s minus three 100s is 100. And then 59 minus 50 is nine. So we would get the same result. The thing to appreciate is that this is all about subtracting 352 from 461 and that there's multiple ways of calculating this.
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