Fractions for Parents part 2
Fractions for Parents part 2 by www.guruparents.com
This video is a quick refresher for parents on multiplication and division of fractions.
Multiplying fractions is nice and easy. Here's an example. What's two thirds times six sevenths? All you do is multiply the numbers on top - the numerators, 2 times 6 is 12. And the denominators, the numbers on the bottom. 3 times 7 is 21. And that's it the answer is 12 over 21. Easy!
Multiplying mixed numerals requires a little bit more work - first you convert them to improper fractions.
2 1/2 x 3 2/3
2 times 2 is 4, + 1 is 5, so this becomes 5/2.
3 times 3 is 9, plus 2 is 11. So this becomes 11/3
5/2 x 11/3
Now, we proceed as in the first example.
5 times 11 is 55
3 x 2 is 6.
55 over 6. And finally, I’ll simplify this. How many times does 6 go into 55? Well 9 sixes are 54, so it’s 9, with 1 sixth left over. 9 and a sixth.
Whole number by fraction
Sometimes kids can get confused with a qustion like this: What is 7 x 3/5.
The key is to remember that 7 can also be written as 7/1 – and now it looks much easier.
7 times 3 is 21. 1 times 5 is 5. 21 over 5. And since 5 goes into 21 4 times with 1 left over, it’s 4 and a fifth.
Of
Another little thing that is worth reminding kids is that you can replace ‘of’ by the mulitplication sign.
A question, written out in words like “What is a quarter of three quarters” can appear confusing until they realise it can be written much more simply and that ¼ of ¾ is the same as ¼ x ¾ - 1 times 3 is 3, 4 times 4 is 4. A quarter of ¾ is 3 sixteenths.
Division of fractions sounds as though it will be hard – but in fact it’s completely simple.
Take this example.
3/5 divided by 2/3.
All you do is flip the second fraction over, more formally this is known as taking the reciprocal of the fraction and multiply.
So flipping 2/3 over we get 3/2 and now we can switch the divided by sign to multiply and proceed as normal.
3 times 3 is 9, 5 times 2 is 10, the answer is 9 tenths.
As with multiplication, if a whole number is involved, remember it can be rewritten as itself over 1.
So, 7 divided by 2/3 is really 7/1 divided by 2/3, which is the same as 7/1 times 3/2. 7 3s are 21, 1 2 is 2. 21 over 2. Or, 10 and a half.
People can get confused when dividing by fractions – it can be a difficult concept. The idea that 3 divided by a half is 6 is confusing. Yet it is the right answer. 3 divided by a half, we flip the ½ and it ends up being 3 times 2; which is 6.
One way to clear things up with your kid is to use an example with pizzas.
Another way of saying what is 3 divided by ½ is how many times does a half fit into 3. So here we have 3 pizzas, how many halves do we have? Clearly it is 1 2 3 4 5 6 halves. 3 divided by a half is 6.
That’s it – hope you enjoyed the video and that it reminded you that fractions aren’t as difficult as they’re made out to be!
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