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Year 7 maths teacher help please

(14 Posts)
Balletgirlmum Fri 22-Apr-16 23:49:10

Ds has been upset tonight because he can't do his maths homework (background is he goes to a selective school but has been having problems as he has asd & school has little experience in Sen.)

However he is desperate to stay at the school & wants to prove he deserves to stay there.

He has to make up his own Think of a Number Problem. They've been doing them in class but he hasnt managed to do one right yet. There must be some formula or logic behind them must there?

He's not allowed to have two additions/divisions etc next to each other or have two opposites next to each other eg plus 1 minus 1 is not allowed neither is divide by 2 divide by 10 but plus 3 divide by 2 is.

noblegiraffe Sat 23-Apr-16 10:35:00

Is he supposed to be using algebra?

Think of a number (n)
Add 2 (n+2)
Multiply it by 3 (3n+6)
Subtract the number first thought of (2n+6)
Halve it (n+3)
Subtract the number first thought of (3)

The answer is 3

Balletgirlmum Sat 23-Apr-16 17:23:19

I don't think I understand.

pizzatray Sat 23-Apr-16 17:36:47

When you ask about the formula or logic maybe you need BODMAS?

noblegiraffe Sat 23-Apr-16 17:45:04

What do they mean by 'think of a number problem'?

Balletgirlmum Sat 23-Apr-16 17:50:39

He has to come up with s list of sums that begins with think of a number & ends with the phrase - the answer is ..... Or is that your original number.

noblegiraffe Sat 23-Apr-16 17:56:06

Yes, that's what was in my post, if he uses algebra like in my post it becomes a lot easier. Does he recognise what's going on in my post?

DesertOrDessert Sat 23-Apr-16 17:58:24

So noble's one will work.

Sentences are
Think of a number
Add 2
Multiply by three
Subtract the number you first thought of
Halve it
Subtract the number first thought of

The answer will always be 3.

Balletgirlmum Sat 23-Apr-16 17:59:06

He understands how to do the sum but can't work out how to make his own original problem up or understand why the end sum is always 3.

DesertOrDessert Sat 23-Apr-16 18:05:30

That why, instead of using actual numbers, Noble has used n
You carry out some steps, and then work out how to get back to just a number, or just n, and that will by your answer for any value of n.

Verybasic one:
Choose a number (answer:n)
Double it (answer 2n)
Subtract the number you first thought of (2n-n=n)
Your answer is what you first thought of.
Can he follow that?

Balletgirlmum Sat 23-Apr-16 18:17:33

Ill show this to him when the match is over & see if it makes sense.

It all looks very complicated for year 7!!

lougle Sat 23-Apr-16 18:30:36

What he needs to understand is that the maths problem is like taking a journey and retracing your steps. So whatever he tells you to do to the number, he has to tell you to undo again later. The really clever number quizzes do that in a couple of steps so it isn't obvious, because 'add 4' followed by 'take away 4' takes away the mystery.

So, using noblegiraffe's example, the reason the answer will always be 3 is this:

Step 1: Think of a number (n) [it doesn't matter what this is because you'll be taking it away from the total later!]

Step 2: Add 2 (n+2)
Step 3: Multiply it by 3 (3n+6) [So you've got 3 lots of your original number, plus 6]
Step 4: Subtract the number first thought of (2n+6) [You've got rid of one lot of your original number but have kept 2 lots and the 6]
Step 5: Halve it (n+3) [You now only have one lot of your original number and 3]
Step 6: Subtract the number first thought of (3) [It doesn't matter what the original number was - it's gone and all you have left is 3!]

The answer is 3

So that's what he's got to do. Come up with a sum where no matter what number you start with (we call this 'n'] you either end up with a specific number as the answer or the original number toy started with.

Balletgirlmum Sat 23-Apr-16 18:45:41

Thank you for hopefully avoiding a meltdown.

I'll do my best to ensure he understands (1:1 is often easier than a class situation)

Balletgirlmum Sun 24-Apr-16 18:35:28

Thank you so much for the explNations in a way we both understand.

Mission accomplished.

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