HBS sample maths question

[fatbananas]

Hi,

I've just seen this link on another thread and I was interested in the maths questions. I've got my head round the second octopus question but the first question (page 7) looks like a sort-of sudoku-type puzzle. I'm useless at those. Can anyone advise me on a technique for answering this type of question?

http://www.zoobuilder.co.uk/admin/clien" onclick="window.open(this.href);return false; ... 012-13.pdf

If questions like these are the norm(living in a super-selective area myself), I'm beginning to think I will be way out of my depth tutoring DS myself ...

[hermanmunster]

FB - I don't think the link works - can you check it?

[fatbananas]

http://www.zoobuilder.co.uk/admin/clien ... 012-13.pdf" onclick="window.open(this.href);return false;

Hope this link works. No wonder I can't do the maths ...

[Guest55]

A hint:

The numbers 1 to 9 add up to ....

However 1 , 4 and 2 appear in two rows so we need to add on 7 which gives us ....

The total divided by 4 is ....

So if we subtract 1 and 4 we know the missing number is ....

[fatbananas]

Ok, I'm putting myself up here for anonymous public humiliation but I still don't get it ...

The numbers 1 to 9 add up to ....

Do you mean:
1+2+3+4+5+6+7+8+9 = 45

Why do we need to add all those together?

However 1 , 4 and 2 appear in two rows so we need to add on 7 which gives us ....

I can see that 1+4+2=7 but do not understand why we need to 'add on7'.

Anyway, so

45+7=52

The total divided by 4 is ....

I can see that there are 4 rows, so 52 ./. 4 =13

So if we subtract 1 and 4 we know the missing number is ....

13-5=8

And then I can put all the numbers in. So the missing answer requested is '8' (if I've done the above correctly); then, inbetween the 4 and 2 is '7' (because all lines have to add up to 13) and I then worked out that the line beginning with 2 would have to have '6' and '5' in it to add to 13 and the line ending with 1 would have to have '9' and '3' in it to add up to 13. And then I've used all the numbers. So I can see that it does work, but I don't know why you have to do the adding 1-9 bit and then adding on '7' (from the numbers already given). What am I doing when I do those two things?

Sorry, I know it's me. I can't even blame sleepless nights up with babies and too much wine and age because I couldn't do this sort of thing when I was lying in, going to the gym and 21!

[hermanmunster]

You are trying to find the total for each of the four arms - easiest way to do this is the total for the whole lot - ie add numbers 1-9 together, but they have helpfully shown that 1,4 and 2 need to be counted twice - hence add 7. Then you can find out (as you did ) that each arm should be 13.

[fatbananas]

Thanks for your reply, Herman: it's becoming a little clearer. I now understand why you have to add 1-9 to find the total of all the squares, but still don't 'get' why you have to add 1, 4 and 2 twice. Doesn't that distort the numbers? I'm sorry: I know it's like pulling teeth. I did get a very good degree in a non-maths related subject

[hermanmunster]

the people who have set the question have put 1 4 and 2 at the "elbows" of the puzzle - each elbow is part of 2 arms in this case so they must be counted twice.

so ultimately the numbers you have to add up are:

1) 9+3+1
2) 1+8+4
3) 4+7+2
4) 2+6+5

Don't worry about not getting it straight off - we all think differently. I have never had any trouble with these sort of things but was never any good at sentence construction or being literate in any way. Still aren't and it isn't helped by always writing things in short txt spk these days

[fatbananas]

Ok, now I completely get it . Talking about arms makes perfect sense to me. Not sure I got beyond counting limbs, really! Thanks so much for taking the time and for being patient!

[omismum]

Interesting puzzle ...how about Octopus question? did u work it out?
many thanks