Maths Q help!!

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Roz12
Posts: 118
Joined: Wed Nov 02, 2011 10:45 pm

Maths Q help!!

Post by Roz12 »

Hi all,

Please help me explain this to my ten year old.

When two fifths of class are absent, there are 18 absent. What is total number of children in the class?

Thanks all
Roz12
Posts: 118
Joined: Wed Nov 02, 2011 10:45 pm

Maths Q help!!

Post by Roz12 »

Hi all,

Please help me explain this to my ten year old.

When two fifths of class are absent, there are 18 present. What is total number of children in the class?

Thanks all
aliportico
Posts: 888
Joined: Wed Aug 01, 2007 12:19 pm

Re: Maths Q help!!

Post by aliportico »

If 2/5 are absent, what fraction of the class is present?

1 - 2/5 = 3/5

So now you know three fifths of the total number = 18.
What is one fifth?

18 / 3 = 6

The whole class is five fifths, therefore total class size = 5 x 6 = 30
aliportico
Posts: 888
Joined: Wed Aug 01, 2007 12:19 pm

Re: Maths Q help!!

Post by aliportico »

Oh, I looked at both, assumed you had corrected absent to present, and then replied to the wrong one!

You can edit your post using the button at bottom right.
Kingfisher
Posts: 416
Joined: Wed Sep 05, 2012 7:08 pm

Re: Maths Q help!!

Post by Kingfisher »

From Kingfishers age 11 daughter:

2/5 = 40% of class
Therefore, 18= 60% of class
18 divided by 6= 3
So 10% = 3
Then you just multiply 3 by 10 to get 30.

Hope I helped :D
Kingfisher
Posts: 416
Joined: Wed Sep 05, 2012 7:08 pm

Re: Maths Q help!!

Post by Kingfisher »

From Kingfishers daughter:

So we know 2/5 = 18.
Divide 18 by 2 to get 1/5, which is 9.
Then you just multiply 9 by 5, and so the answer is 45.

:D
IronMikeTyson
Posts: 612
Joined: Wed Nov 23, 2011 1:52 pm
Location: Shamballa

Re: Maths Q help!!

Post by IronMikeTyson »

No the answer is 30.

3/5 are present.

3/5=18
"To err is human;to forgive ,divine"
Kingfisher
Posts: 416
Joined: Wed Sep 05, 2012 7:08 pm

Re: Maths Q help!!

Post by Kingfisher »

Roz12 wrote:Hi all,

Please help me explain this to my ten year old.

When two fifths of class are absent, there are 18 absent. What is total number of children in the class?

Thanks all
When two fifths of class are absent, there are 18 absent.

I think perhaps you misread the second absent as present.

Also I think Roz12 was slightly confusing by posting almost the same question twice, one reading When two fifths of class are absent, there are 18 present.

The mistake is understandable :)
Roz12
Posts: 118
Joined: Wed Nov 02, 2011 10:45 pm

Re: Maths Q help!!

Post by Roz12 »

Hi all

yes I did post the message incorrectly but I now know about the edit button!!

Thanks
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