This series of 3 minute math is designed as a quick reminder for some of the main topics – including how to subtract fractions. I hope they help to provide a focus and a way forward. If you need any more detail please search the site or contact me – always pleased to answer any questions!
All the very best with your studies.
Transcript from the video:
“Welcome to three minute math. This video is all about how to subtract fractions.
The thing you need to remember with subtracting fractions is that the denominators (numbers at the bottom) have to be the same.
It's fairly straight forward if you get a question which is something like:
The denominators are the same so the answer is .
However it's also good to see if you can reduce using division. I'm going to divide the top and the bottom by two so I reduce this fraction to .
Okay, so let's make it a little bit more complicated, let's take:
All we do is we take away the big numbers first. Six take away one is five then:
. Then reduce to .
…and the answer is going to be .
If the denominators are different, we need to make them the same, so let's have a look at a question like this:
The way I'm going to make the denominators the same is I'm going to make them both over twelve
Three times four is twelve, multiply the top by four which is eight. Then four times three is twelve, so I multiply the top by three. Eight take away three is going to be .
…which is the answer to this question.
The same applies if we've got something like:
seven take away two is five
I've already worked out
so the answer would be:
This is more typical of an exam paper question but just occasionally you're going to get an exam paper or an exam question, which is going to be slightly tricky. You may get something like:
Well, that's okay because we're going to make sure the denominators are the same.
So let's just have a look at that…
three and ‘something over twelve' minus one and ‘something over twelve'
four times three is twelve, so therefore three times one is three
three times four is twelve so four times two is eight
Okay, so I can take away the numbers but – I can't do that. It's really important that you recognise this when you're doing this sort of exam paper question.
What I'm going is I'm going to deal with the three and just completely ignore everything else.
The three, I'm going to change into
which is exactly the same as 3 … but if I add that to the which I've got here, then I'm going to be in a position to make it
Now it means when I take away the I'm in a much stronger position to be able to do it:
two take away one is one, and
and that would be the answer to this tricky exam paper question.
Okay, so this has been three minute math – if you want any more information search on the channel, where you'll find loads of videos and lots more detail.
Hope it's been helpful. Look forward to seeing you inside the next three minutes.”
Watch video on YouTube – 3 Minute Math – Subtract Fractions
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