### Video instructions and help with filling out and completing Why Form 2220 Subtracting

Instructions and Help about Why Form 2220 Subtracting

G'day and welcome to the tech math channel in this video we're going to be having a look at as a way of adding two fractions together and then or subtracting two fractions from each other where we have different denominators different bottom numbers so I'll show you how to do this it's a really really simple method and this is the way I usually show my students scores saves a lot of hassle so say for instance we have a fraction like this half and we want to add to that 1/3 to do this really really simply this is what we do okay so he legals and I'll put that line there what we do is this to get the bottom number first off what we do is we multiply these numbers so 2 times 3 is 6 pretty easy and then what we do is we start at the top left here and we multiply this number by the diagonal here okay so it's diagonal bottom number here so 1 times 3 is 3 we use the same sign as a which is a plus then we go to the right number here now at the top and we multiply this number by this number 1 times 2 is 2 okay equals 3 plus 2 is 5 and look at the bottom number is 6 and there you go we've got 5 6 that's the easiest way of doing these ok so anyway I'll put another one up hopefully you got that one alright I'll get another another fraction what about we go something a bit different we go 1/4 and I'll put what about something like 2/3 and that equals all right let's have a look I'll get this pin here and again we'll work at the bottom number we multiply these 4 times 3 is 12 we get this number here the top left and we multiply it by this number which is a three use the same sign multiply this number by this one okay 2 by 4 is 8 8 plus 3 is 11 over 12 yeah you get that all right I reckon a few more examples because we're going to do a few subtraction ones in a minute also you'll notice with a few of these are there they're there they're most simple armed and so a couple of these you can simplify a bit further let's have a look we'll see we can get 1 so what about if I add 1/2 to 3/4 hopefully this will work and what we do is again you might give this one a go before I start yeah you might a pause it and give it a go hopefully you did so what we do is we go two fours 8 start at the left it's really important you start the left by the way I'm not starting over here on my way starting over here you'll notice 1 times 4 is 4 we use the plus 3 times 2 is 6 okay so 4 plus 6 is 10 and then we get 10 eighths now what you're going to notice first off is that we can simplify this further so let's do this first off we look for a number that goes into both the top and the bottom and you'll see straight away that number is 2 so we divide the top by 2 we get 5 we do either bottom by 2 we get 4 we can still simplify this this is at the moment what we call and improper fraction we can turn it into a proper 4 into a mixed number that is and the way we do this is we go 5 divided by 4 because if this peak this top number is bigger than the bottom number you can do this 5 divided by 4 is 1 and 1 left over we put that 1 over the bottom number which is 4 okay I reckon another one okay hopefully these are not a problem and hopefully you're picking them up really really easy I must have always wondered why they teach our fractions really difficult difficult often get a lot of students come in and they've done fractions three or four times and different in their school career and they still don't get it and it's actually a little bit annoying oh yeah so anyway I'll shut up and I'll keep going so what about we do 3/4 and we model multiply we're not going to multiply we're going to add that to 1/3 all right what does that equal get the bottom number three fours 12 start up here three fours and nine we go plus one four is four we end up with 13 3 plus 4 is 9 plus 4 is 13 over 12 that we can simplify further because we have it this number here is bigger than this number and then so we divide 12 into 13 12 goes into 13 once 1 remainder 1 over 12 okay what about if we start with we could do this subtraction 1 okay what about that we do 3/4 takeaway now what about 1/3 okay it's the same sort of thing and this is where it becomes really important that you start in a second in this top left in a little bit so first off we go 4 3 2 12 and this is where this becomes important you start over here 9 3 is 3 3 is a 9 use the minus 1 4 is 4 9 take 4 is 5 this goes over 12 we have our answer now just one little variation on this by the way I think this is a good thing to get but I might even arm I won't be able to do this straightaway but I'll put a link up to this and this is where are we looking at how to if.