Subtracting Fractions 2
Subtracting with mixed numbers is normally just the same as adding.
The only problem comes when the second fraction is smaller.
Here is an example of this sort of take away sum.
Write out the question
Subtract the whole numbers
Put down the LCM
Do the "Not thinking very much at all" line
Work out what has happened to the bottoms
Do the same to the top as we did to the bottom
Write in the top values
Now we're in trouble!
All we do is the same as for a normal take away question and borrow.
We steal a whole one from the three but because we are doing fifteenths
that whole one becomes 15 fifteenths:
Now we can complete the question:
Borrow from the 3
Add the 15 fifteenths to the 3 that are already there
Take away the tops
Don't subtract the bottoms!
The only problem comes when the second fraction is smaller.
Here is an example of this sort of take away sum.
Write out the questionSubtract the whole numbers
Put down the LCM
Do the "Not thinking very much at all" line
Work out what has happened to the bottoms
Do the same to the top as we did to the bottom
Write in the top values
Now we're in trouble!
All we do is the same as for a normal take away question and borrow.
We steal a whole one from the three but because we are doing fifteenths
that whole one becomes 15 fifteenths:
Now we can complete the question:
Borrow from the 3Add the 15 fifteenths to the 3 that are already there
Take away the tops
Don't subtract the bottoms!
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