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## 4th grade

### Course: 4th grade > Unit 5

Lesson 8: Multi-step word problems# 2-step estimation word problem

Sal uses estimation to solve multi-step word problems involving addition, subtraction, multiplication, and division.

## Want to join the conversation?

- I do i figure all of this out? on the final test I keep getting aanswrs wrong!(18 votes)
- Minor spelling issue(3 votes)

- we are told a teacher bought 12 sheets of stickers to use on the homework of her students each sheet had 48 stickers at the end of the year the teacher had 123 stickers remaining which is the best estimate for the number of stickers the teacher used so like always pause this video and see if you could have a go at this before we work on this together alright now let's work on this together so the first thing to appreciate is we just have to figure out an estimate we don't have to figure out the exact number of the stickers that were used let's see if we can do that so let's see we have 12 sheets of stickers and each sheet had 48 stickers 48 stickers per sheet so how many stickers did the teacher start off with well there were 12 sheets times the number of stickers per sheet so times 48 times 48 this is going to be the number that they started off with number to start and then if we want to figure out the number that are used we just have to figure out okay from the number that was started how many are left over and then that's how many were used and so how many were left were left over well 123 were remaining at the end of the year so that's this number right over here so if we calculate that first the number to start we subtract out the number that are remaining then that will be equal to the number of stickers that the teacher used now once again we don't have to figure out exactly we just have to estimate and so I'm just going to try to figure out friendlier numbers to work with so instead of 12 let's imagine let's imagine actually I'll stick with 12 12 I can work with but let's say that this is going to be approximately equal to so in parenthesis instead of 48 I'll say it's roughly 50 so this is going to be approximately 12 times 50 instead of 123 I'll say that's roughly a friendlier number might be a hundred and twenty or might be a hundred that's just 220 so minus 100 we could have done a hundred and so we could figure out what this is in our heads or with a little bit of paper 12 times 5 is 60 so 12 times 50 is 600 and then 600 if we had a hundred-year 600 minus 100 movement at 500 or 600 minus 120 is 480 so what we want to do is look in the choice and see which of these choices is closest to roughly 500 or roughly 480 and so let's see out of all of these actually they have exactly 480 which is so they estimated exactly the way we happen to estimate now not every person is going to do that we could have two chosen instead of hundred 23 becoming 120 in our estimate we could have put a hundred there and then we would have gotten 500 but even if 500 was our estimate 480 still would have been the closest to that estimate, i love khan academy it is very easy when khan academy explain and david alway says david out(8 votes)
- You wrote A LOT..(10 votes)

- i hardly understand this i had to watch it 4 times to under stand it(10 votes)
- Sal and all the khan members are really smart I truly love how

they work.(7 votes)- Aww... That's kind.😉(7 votes)

- why did he spell slart(9 votes)
- I cant do long divison(4 votes)
- for best, try to use long divison with a paper or somethhin(7 votes)

- how do u do this(6 votes)
- how are you so smart(6 votes)
- Word Problem

A drama group has 90 minutes to practice two scenes. They want to practice the pirate scenes 4 times, and ech time takes 15 minutes. The mermaid scene takes 7 minutes.**How many full times can the group practice the mermaid scene**?

Type in answer in comment or answer below. :) HAVE FUN!(4 votes) - This doesn't really make sense(4 votes)

## Video transcript

- [Instructor] We are told
a teacher bought 12 sheets of stickers to use on the
homework of her students. Each sheet had 48 stickers. At the end of the year, the teacher had 123 stickers remaining. Which is the best estimate for the number of
stickers the teacher used? So like always, pause this
video, and see if you can have a go at this before
we work on this together. All right, now let's
work on this together. So the first thing to appreciate is we just have to figure out an estimate. We don't have to figure
out the exact number of the stickers that were used. Let's see if we can do that. So let's see, we have 12 sheets of stickers, and each sheet had 48 stickers, 48 stickers per sheet. So how many stickers did
the teacher start off with? Well, there were 12 sheets times the number of stickers
per sheet, so times 48, times 48. This is going to be the number
that they started off with, number to start. And then if we want to figure
out the number that are used, we just have to figure out, okay, from the number that was
started, how many are left over? And then that's how many were used. And so how many were left over? Well, 123 were remaining
at the end of the year, so that's this number right over here. So if we calculate that
first, the number to start, we subtract out the
number that are remaining, then that will be equal
to the number of stickers that the teacher used. Now once again, we don't
have to figure out exactly. We just have to estimate. And so I'm just going to try to figure out friendlier
numbers to work with. So instead of 12, let's imagine, let's imagine, actually,
I'll stick with 12. 12 I can work with. But let's say that this is going to be approximately equal to, so in parentheses, instead of 48, I'll say it's roughly 50. So this is going to be
approximately 12 times 50. Instead of 123, I'll say that's roughly, a friendlier number might
be 120 or might be 100. Let's just do 120, so minus 120. We could've done 100. And so we could figure out
what this is in our heads or with a little bit of paper. 12 times five is 60,
so 12 times 50 is 600. And then 600, if we had 100 here, 600 minus 100 would've been 500, or 600 minus 120 is 480. So what we want to do
is look at the choice and see which of these choices is closest to roughly 500 or roughly 480? And so let's see, out of all of these, actually they have exactly 480, which is, so they estimated exactly the
way we happened to estimate. Now not every person is going to do that. We could've chosen, instead of 123 becoming
120 in our estimate, we could've put 100 there, and
then we would've gotten 500. But even if 500 was our estimate, 480 still would've been the
closest to that estimate.