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 Post subject: can somebody please explain these!Posted: Tue Sep 11, 2007 1:42 pm
Over the weekend my dd attempted her first maths nfer paper, on which she scored 78%, which i thought wasn't too bad for her first try.Could anybody explain the best way to tackle the ones she got wrong, many thanks.

hanif will be x years old 7 years from now
how old was he 7 years ago

craig is arranging plates of food for a party.
he has 3 types of sandwich,2 types of cake,and 4 types of biscuit.

which shows the number of possible combinations of sandwich,cake and biscuit on a plate

(3x2)+(3x4)
3x2x4
(3x4)+(2x4)
3+2+4
(2x3)+(2x4)

and last but not least(sorry)
question 41, which shows a flat shape with the shaded corners cut out and you are asked to find the capacity once it is folded into a small open box.The dimensions are 8cmx6cmx6cm.
the answer they give is 16cm3

truly grateful and exhausted lol

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 Post subject: Posted: Tue Sep 11, 2007 2:38 pm

Joined: Fri Mar 17, 2006 5:12 pm
Posts: 1348
Location: Birmingham
Hi 0505

Question 1

If Hanif will be x years old in 7 years time, that means he will be (x-7) today.

It follows therfore that 7 years ago he was (x-14) yeasr old.

Question 2

I remember this with my son a few years ago - he was confused as the question was ambiguous. I believe they intend the children to deduce that the plate can contain anything from 1 item (of any description) to a plate containing sandwiches, cakes and biscuit (of any type).

In this situation the number of combinations is (b) 3 x 2 x 4

I would worry about the last question, I don't think it's well written. My son is very good a maths (in year 8 at grammar now) and he struggled with this type of question - it's often the good mathematicians that struggle with this type of badly written question.

Hope this helps

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 Post subject: Posted: Wed Sep 12, 2007 9:48 am

Joined: Thu Jan 12, 2006 3:29 pm
Posts: 625
Hi KenR

The third question

This is a net of 8x6 not 8x6x6
A square of 2x2 has been removed from each corner.
When the sides are folded up it creates a box
4x2x2
=16cm3

Regards

Mike

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 Post subject: Posted: Wed Sep 12, 2007 12:23 pm
Hi Mike

Sorry to be a pain but can you explain the 'Hanif's age' answer and how you work it out. I cannot see why the x means 7 why can it not mean any other number.

These were never my thing at school and I struggled with them two years ago when I was tutoring my son and am worried as I will be tutoring my daughter soon. If I don't get them how will I explain them to my little girl?

Help

Mel

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 Post subject: Posted: Thu Sep 13, 2007 8:18 am
x does not mean 7. x represents any number. Take an example

If Hanif will be 30 in 7 years time, then he is 23 now, and was 16, 7 years ago. In other words, 30-7-7 or 30-14.

If Hanif will be 52 in 7 years time, then he is 45 now, and was 38, 7 years ago. In other words, 52-7-7 or 52 -14.

The x is taking the place of the 30 or 52, and actually can't equal less than 14 because it is impossible to have a negative age.

The point of using x instead of 30 or 52 or any other age greater than 14, is that it gives you an equation for all cases within the limits. This is the whole point of algebra, to give you a one-liner that sums up what would otherwise take several sentences to explain.

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 Post subject: Posted: Thu Sep 13, 2007 10:53 am
Hi Jah

Sorry but on the actual question it didn't state what age he would be, taht woudl ofcourse make it simpler, it just said

hanif will be x years old 7 years from now
how old was he 7 years ago

So how do you get the answer???

Mel

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 Post subject: Posted: Thu Sep 13, 2007 11:03 am
Isn't the answer x-14 as per KenR's explanation?

I haven't seen the whole quetion but on reading what was asked, am inferring the answer will be in algebraic form and not a whole number as you expect.

Correct me if I'm wrong..

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 Post subject: Posted: Thu Sep 13, 2007 11:10 am
Now that makes sense

Mel

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 Post subject: Posted: Thu Sep 13, 2007 11:34 am
MelX

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 Post subject: Posted: Thu Sep 13, 2007 12:31 pm
Mel is certainly not the only one struggling with that particular question.

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