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PostPosted: Fri Aug 31, 2007 8:30 am 
could somebody please explain the right way to show my dd this question thanks.

When i was born my aunt was 21 years old.At my next birthday my aunt will be four times as old as i will be. How old will i be at my next birthday.

I know the answer is seven but i need to find a quicker way to show my dd.


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PostPosted: Fri Aug 31, 2007 9:06 am 
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Joined: Mon Jun 18, 2007 2:32 pm
Posts: 6966
Location: East Kent
how about a number line? Show it visually, I often draw diagrams to help me work out word problems.


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PostPosted: Fri Aug 31, 2007 10:05 am 
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Joined: Sun Dec 04, 2005 3:47 pm
Posts: 1348
Location: Berks,Bucks
This is how I would do it:

'my age' + 21 = 'my aunt's age'
so
'my aunt's age' - 'my age' = 21

In addition,
'my aunt's age' = 'my age * 4

Replace 'my aunt's age' with 'my age' * 4 in
'my anount's age' - 'my age' = 21

You get
'my age' * 4 - my age = 21
so
'my age' * 3 = 21
'my age' = 7


Hope this helps

Catherine


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PostPosted: Fri Aug 31, 2007 12:40 pm 
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Joined: Fri Jul 06, 2007 8:31 pm
Posts: 1192
0505 wrote:
i need to find a quicker way to show my dd.


Age next B'Day N; Aunt will have aged by N years... so age will be 21+N

N = ( 21 + N ) / 4

4N = 21 + N

3N = 21

N = 7

Potentially a confusing question. Definitely worth checking the answer by substituting back.

_________________
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PostPosted: Fri Aug 31, 2007 1:28 pm 
The answers given above all use algebra, which is great, but isn't usually the way 11 year olds think (at least those from state schools). Kids on the other hand are usually very good at working out how old someone will be when they are a few years older. I would expect my 11 year old to scribble out the following to solve this problem:

Me Aunt
0 21
1 22
2 23
3 24
4 25
5 26
6 27
7 28

This takes only a few seconds, and the answer leaps out.

Hilda


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PostPosted: Fri Aug 31, 2007 2:51 pm 
I agree with Hilda. While the other methods are sound algebraically, trial and error would probably produce a quicker answer, especially if they have a 'feel' for maths and could make a decent initial guess which they would then adjust. I have some old Maths Challenge books I use (out of print) and they positively encourage guessing, but in an orderly fashion by drawing a quick little table.If you're exam in multiple choice, then you'd want to go for substitution of answers.


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PostPosted: Fri Aug 31, 2007 3:02 pm 
thanks for the quick replys, Hilda that is the way i worked it out but knew it was an algebra question so thought there would be a quicker explanation but all it did was confuse me more!.May stick to the this way for now


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