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Current time:0:00Total duration:4:34
CCSS.Math:

Video transcript

there is a half an apple pie left you want to eat twice what your little brother eats but you also need to save a slice for your mom you can cut her slice that it's 30 degrees what is the measure of your piece of the pie in degrees so to tackle this we just have to remember a few things we have to remember that degrees in a circle so if we were to go all the way around a circle that that would be 360 degrees 360 degrees but we only have half a pie here and actually let me draw it a little bit differently so if we had a whole pie so if we started here and if we had a whole pie we went all the way around that would be 360 degrees but we only have a half pie so we only have 180 degrees and let me do that in a color you're more likely to see it's hard to see as well we only have 180 degrees of pie left but let's just keep that in mind and think about how we're going to split it between ourselves our brother and our mom so let's define some variables let's let X be equal to the degree measure of my brother's pie or you brought your little brother's pie so this is degree measure of brother's pie brothers pie and then what would the amount of pie you eat be what says you eat twice what your little brother eats so 2x would be equal what you eat what you eat it's really the degree measure of what you eat and then how much does your mom eat well it says you cut her slice that is 30 degrees so your mom's gonna get a 30 degree slice gonna get a slice something like that so the amount that your brother eats X plus the amount you eat plus the amount that your mom gets plus 30 degrees is going to be equal to this 1/2 pie and remember all of these are degree measures so it's going to be equal to 180 degrees and just to visualize it over here and let me do it down here where it's easier to see it we have half a pie that we're dealing with we're gonna save 30 degrees we're going to save 30 degrees for our mom so that's 30 degrees right over there your brother is going to eat some amount your brother is going to eat some amount so that is X and then you're going to eat twice that amount so that is 2x X is the measure of this this angle and then 2 X is a measure of that angle so you see that 30 degrees plus X plus 2 X or X plus 2 X plus 30 degrees is going to be equal to 180 degrees now we can simplify this if we have one of something and then have another two of it how much do we have now well I now have three X's so 1 X plus 2 X's is going to be 3 X's so I have 3x plus 30 degrees plus 30 degrees plus 30 degrees is going to be equal to of course 180 degrees 180 degrees now to solve for X we can subtract 30 degrees from both sides so minus 30 degrees minus 30 degrees and I could have just written that I could have all assumed that I'm doing it in degrees and just done it at the end but I'm just keep writing it so I'll just keep going with that and then we are left with we are left with 3 X 3 X equaling 180 degrees minus 30 degrees is equal to 150 degrees 150 degrees and now we can just divide both sides by 3 and divide both sides by 3 and we're left with X equaling 150 divided by 3 is 50 degrees X is equal to 50 degrees now we have to be careful X is not the is not what they're asking for they're asking for the measure of your piece of pie in degrees X is the degree measure of your brother's piece of pie what you eat is 2 times that so if X is 50 degrees if X is 50 degrees 2 times that is going to be 100 degrees so what is the measure of your piece of the pie in degrees it is going to be 100 degrees so if we draw our pie again if we draw our half pie you have 30 degrees for your mom so that's 30 degrees for your mom you have 50 degrees for your brother you have 50 degrees for your brother and then you have twice that for yourself 100 degrees