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## 4th grade

### Unit 12: Lesson 1

Understanding angle measurement# Angles in circles word problem

Lindsay solves a word problems about angles as part of a circle.

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## Video transcript

- [Voiceover] If Arianna
turns the stove dial 135 degrees to the right, what setting will the dial be on? So two very important things up here. First she's turning the dial 135 degrees. And which way is she turning the dial? She's turning the dial to the right. So here's our dial it's facing up. This red dial right here. Facing up sort of like on a clock. And we're going to be turning
the dial to the right. And how far to the right? 135 degrees. So this dial will turn until
it's reached 135 degrees. So how can we figure out if we start turning this dial when to stop? When it's reached 135 degrees. Well, one common way would
be to use a protractor. We could set up our protractor, measure out 135 degrees. But in this case we can't do that 'cause we don't have a protractor. So let's use some other information. Some other stuff we know about angles to see if we can solve this. One thing I know, one
angle that we see a lot is a 90 degree angle. And a 90 degree angle if we start up at the top like our dial and turn 90 degrees, we're gonna end up with
an angle like this. An angle where we could put a square in the middle and finish the square. Well it's like a square angle. So this is a 90 degree angle. So coming over to our dial, if we start at the top
and we go 90 degrees. So we start here at the
top and we go 90 degrees, we'd end up on the low setting. 90 degrees. But we're not going 90 we're going 135 which is more than 90 degrees. So here's one clue. We know we're going farther
than the low setting. We don't know how much farther. We're definitely gonna
go past the low setting. Another angle I could use to help me is the straight angle. 180 degrees. If 180 degree angle again starts at the top like our knob is currently. Like our dial. It will go all the way around until we have a straight angle like this. So again, looking at our knob, if we started at the top and we went around 180 degrees, we would end up facing
straight down at medium. This would be 180 degrees. So where does 135 fall? Well 135 falls somewhere
in between 90 and 180. 90 was not far enough of a turn. And 180 was too far of a turn. So we want something in the middle. And what setting is in the middle of the 90 and the 180? Right here in the middle of them is medium-low. So turning our stove to
135 degrees to the right will set our stove to medium-low.