Finding consecutive multiples (10 and 100)
About this video
A number line counts by tens and shows a dot between 8,230 and 8,240 for the number of trees planted. Sal decides the dot is more than halfway from 8,230 to 8,240, so it is closer to 8,240, and about 8,240 trees were planted.
You'll be able to
- find the two tens a number on a number line is between.
- decide which ten a point is closer to by checking the halfway point.
- give a reason for my estimate.
Key words
- number line
- A line with numbers marked in order, used to show where a number fits.
- halfway
- The middle point between two numbers, like 8,235 between 8,230 and 8,240.
- about
- Close to but not exact; an estimate.
Transcript
- [Lecturer] We're told the number line represents the total number of trees planted during a community event. All right, so they put the dot there, and it looks like they're counting by tens. We have 8,210, 8,220, 8,230, and 8,240, and it keeps going, and we're between 8,230 and 8,240.
And then they say, about how many trees were planted? And in every one of these choices, they are giving us either 8,230 or they're giving 8,240, and then they're trying to get us to pick which reason is the reason why you would pick one of those. So why don't you pause this video and work on this on your own before we do this together.
Okay, so the way I'm going to approach it is I'm just going to look at this number line and think about, which of the tens is it closer to? Is it closer to 8,230 or is it closer to 8,240? And we can see that the dot is more than halfway from 8,230 to 8,240. And so it's clearly closer to 8,240.
And so that's the choice I'm going to go with. And let's see if the rationale or the reason, it makes sense, 8,240 trees because the point is more than halfway between 8,230 and 8,240. That's exactly what I said. We know it's not 8,230, but they gave two different reasons for that wrong answer.
We're clearly closer to 8,240.
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