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CCSS.Math:

if I were to ask you what is 5 minus 3 plus 2 what would you say that is pause this video and try to figure that out all right well if you wanted to tackle this you would really just read it from left to right or you would compute it from left to right you'd first figure out what 5 minus 3 is and 5 minus 3 is equal to 2 and so you'd say okay that's going to be 2 plus 2 which of course we know is equal to 4 now what if I were to involve a little bit of multiplication or division if I were to go up to you and I were to say what is 5 plus 3 times 2 pause this video and try to figure that out well you might be tempted to do it in a similar way you might be tempted to say okay I'll just go from left to right I'll first compute what 5 plus 3 is and that of course would be equal to 8 and then I would multiply 8 times 2 to get 16 but it turns out that this would not be the right way to approach this because for very good reasons that will study in perhaps future videos we don't always go left to right especially when we're dealing with different types of operations and the standard way that this is approached is that multiplication and division will be done before addition and subtraction so the way that you would actually compute this is that you would compute the 3 times 2 first so you would say that this is the same thing as 5 plus 6 5 plus 6 which is going to be equal to 11 not 16 so this is going to be equal to 11 so with that out of the way let's do a few more examples let's say someone were to approach you and say what is 9 minus 6 divided by 3 pause this video and see if you can figure that well as I just said we would do multiplication or division before we do subtraction so we'll actually do the six divided by three first and six divided by three is two so this simplifies to 9 minus 2 which is equal to 7 and I really want to emphasize it's important that you get this idea that multiplication and division should be done before the addition or subtraction unless you're given some other types of directions because if you just went left to right here you were to said 9 minus 6 is 3 and then you would have divided that by 3 which you've got which would have given you 1 which is clearly a different number than 7 let's do one more example just just for kicks let's say that someone were to ask you what is 2 times 3 minus 1 pause the video and try to figure that one out well in this one doing our multiplication first is also the same as going left to right first so if we do 2 times 3 first 2 times 3 is 6 so that's 6 and then we would want to calculate 6 minus 1 which is of course equal to 5 so big picture if you just have a bunch of things that are being added subtracted multiplying and divided and there's no parentheses in it you would always prioritize the multiplication or the division over the addition or the subtraction