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PostPosted: Fri Sep 10, 2010 5:48 pm 
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Joined: Mon Feb 16, 2009 7:52 pm
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Hello again,

Can one of you bright sparks help my DS with this question?

Joshua is four times older than his brother Ted.
In four years time he will be twice as old as Ted.
How old is Joshua now?

Many Thanks


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PostPosted: Fri Sep 10, 2010 5:57 pm 
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Joshua is 8. I'm afraid I did it by just selecting a number and seeing whether it worked. I took an educated guess bearing in mind the relationships in the question. I'm sure there is a way of doing it with algebraic equations too.

If your child is doing a multiple choice Maths test then I suggest that he applies each of the possible answers to the question until he find the answer that works ie trial and error


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PostPosted: Fri Sep 10, 2010 6:37 pm 
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Location: caversham
Quote:
Can one of you bright sparks help my DS with this question?


No, not without using simultaneos equations and substitution which seems to hard for 11+.

DS1 says 8 and 2 and 12 and 6, off the top of his head based on my notes of

J=Tx4

J+4=Tx2

So Josh is 8? And T is 2. Try feeding in for T 1, 2 (bingo) :)

Tough question, where did it come from, agree with Twinkle if it is multi-choice substitute the answers.


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PostPosted: Sat Sep 11, 2010 10:06 pm 
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stevew61 wrote:
Quote:

DS1 says 8 and 2 and 12 and 6, off the top of his head based on my notes of

J=Tx4

J+4=Tx2



I rather think that the two equations that we can extract from this story are:
J= 4T
J + 4 = 2 (T+4) so J + 4 = 2T + 8
In this second equation, I use the value of J from the first one:
4T + 4 = 2T + 8
I then minus 2T from both sides: 2T + 4= 8
2T = 4
T = 2
so J= 8

I hope these matematical explanations will help you, though I am not sure a 10 or 11 year old can grasp them! :shock:

Good luck :)


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PostPosted: Mon Oct 11, 2010 9:09 pm 
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The intended method behind the question was trial and error with a good dose of logic. There is no multiple choice on the paper. It was written as practice for the Essex 11+, which is tough!


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PostPosted: Fri Oct 15, 2010 9:15 pm 
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Joined: Sat Nov 21, 2009 8:23 pm
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This kind of problems can be very easily solved by converting the information in the question into a simple equation.

Let the present ages of the children be J (for Joshua) and T (for Ted). Then, we can write an equation as below:

J = 4T.

After 4 years, Joshua will be 4T + 4. Ted then would be T+4.

As per the question, Joshua will be twice as old as Ted after 4 years.

Hence 4T + 4 = 2 (T + 4)

ie. 4T + 4 = 2T + 2 X 4
ie. 4T + 4 = 2T + 8
ie. 4T - 2T = 8 - 4
ie. 2T = 4
ie. T = 4/2 = 2

Hence Ted must be 2 years now and Joshua should be 4 x 2 = 8 years.

Simple equations provide a sure-shot method to reach the answer within seconds instead of the trial and error method. Hence children should be trained to convert the information given in the problem to an equation. Once the equation is writeen, 99 % of the problem is done!

Suria


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PostPosted: Fri Oct 15, 2010 10:10 pm 
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Location: Chelmsford and pleased
It has to be said that when these questions are written for 10 year olds; an indepth knowledge of algebra is not usually expected.


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PostPosted: Sun Oct 17, 2010 6:43 pm 
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i would say joshua is 8


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