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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Original poster

to think that both answers are equally right

36 replies

lorisparkle · 26/02/2016 19:23

The question is....

Complete the sequence

2.5, 3.50, 4.500, ........., 6.5, ....... 8.500, ..........

DS1 and his friend who are both in the top group for maths put this as their answer...

2.5, 3.50, 4.500, 5.50 , 6.5, 7.50, 8.500, 9.50

They were told the answer is wrong - I personally think that it is right and definitely as right as the answer 'in the book'

Which was 5.5000, 7.50 and 9.5000

DS1 got quite upset in class because he would not accept his answer is wrong. So what does everyone think and what would you do?

OP posts:
BlackHillsofDakota · 26/02/2016 19:26

No I'd say you were wrong the pattern is no zero, one zero, two zero etc so if you leave off one of the zeros the pattern isn't correct. I'm not that great at maths though so I could be wrong

moreshitandnofuckingredemption · 26/02/2016 19:27

Depends if it's couched as a maths question or a NVR question. If it's maths I'd put 5.5, 7.5 and 9.5 and expect it to be right (as are your DS' answers). If it's a NVR question then it's more about patterns and I would say the book answer is right.

ScarletOverkill · 26/02/2016 19:29

I agree with BlackHills it's about the pattern of zeroes

DelphiniumBlue · 26/02/2016 19:29

I'd say that the number of zeros is relevant to the pattern but not to the numerical value of the answer.

Icanseeclearly · 26/02/2016 19:29

It is a pattern, your ds went for mathematical which is only part of the answer. Yes he was wrong but, probably, because he is thinking more mathematically than the group are aiming at. Not good now but will prove itself later.

Lweji · 26/02/2016 19:30

It's actually unworkable.
It could be both.

OurBlanche · 26/02/2016 19:31

I think the pattern was supposed to be more established than your DS spotted and they were wrong.

Bear in mind many science exams have "To X decimal places" in the questions and year after year a significant % of students get the sums right but the answer wrong for ignoring that instruction.

But I can see they had 'pyramidded' their answers and might have decided that they had an alternative and equally correct answer.

EduCated · 26/02/2016 19:31

Agree it depends whether it was an NVR or mathematical question. Mathematically totally correct.

NotCitrus · 26/02/2016 19:32

But it's just as good a pattern:
Ds: 0,1,2,1,0,1,2,1...

Book: 0,1,2,3,0,1,2,3....

Ascending and descending is just as patterny as ascending to 3 then starting again!

Quimby · 26/02/2016 19:32

But does the kids answer not also follow a logical pattern?

Ad a zero each time until you have two zeros then take a zero away until you have none
Rinse repeat

cornflakegirl · 26/02/2016 19:32

Loris - I agree - you can't tell whether the pattern of zeroes is 01210121 or 01230123. Would be quite worried about a maths teacher who couldn't see that - or explain why the former is incorrect if I'm missing something.

How old is your DS?

Tantrictantrum · 26/02/2016 19:33

Agree it could be both. Stupid question

Lweji · 26/02/2016 19:33

It doesn't make sense to suddenly drop back to no zeros, so it's equally plausible that there would be a reduction after the 500:
5,50,500,50,5,50,500,50,5
Or
5,50,500,5000,5,50,500,5000

I think whoever set it up was careless.

Lurkedforever1 · 26/02/2016 19:33

As moreshit said, depends if it's a maths or nvr one.

OurBlanche · 26/02/2016 19:33

Lweji, that's right. Without a triple 0 in the question you would be constrained, not introducing a new pattern. So, in that respect, OPs DS was 'more' correct (she says knowing how much that annoys proper Mathists Smile)

EduCated · 26/02/2016 19:33

And actually yes OurBlanche is right, theirs is also a pattern in the number of 0s: none, one, two, one, none.

Chicagomd · 26/02/2016 19:35

This reply has been deleted

Message withdrawn at poster's request.

MsMermaid · 26/02/2016 19:35

Even as part of a pattern I think ds's answer is better. His pattern uses the number of zeros as well.

No zeros, one zero, two zeros, one zero, no zeros, etc. That's a pattern, equally as good (better IMO) as a pattern that increases the number of zeros to an arbitrary point then goes back to no zeros.

arethereanyleftatall · 26/02/2016 19:37

Yanbu.
The pattern could either be pyramid or increasing '0's. It's ambiguous.

Lweji · 26/02/2016 19:39

Wouldn't it be great if the teacher was on MN?

Original poster
lorisparkle · 26/02/2016 19:40

DS1 is in Year 5 and it was in a maths lesson

So those who think DS is equally right - what should I do.

The teacher says that 'There is also a pattern sequence where the number of zero's (sic) increased, this allowed the class to discuss the place value aspects of numbers with decimal points'.

OP posts:
moreshitandnofuckingredemption · 26/02/2016 19:41

Missed the bit about the rising/falling pattern, your son is right as well if it's an NVR question.
I bloody hate NVR, half the time I can have the question and answer in front of me and still not understand it [fick]

Original poster
lorisparkle · 26/02/2016 19:41

I would be highly surprised if the teacher is on MN but you never know!!!

OP posts:
cornflakegirl · 26/02/2016 19:44

A good teacher would have said - excellent work DS! There's another pattern that fits too - can you find it?

OurBlanche · 26/02/2016 19:46

Write it out, as in above posts, and send it in to her. Tell her that these answers also use a pattern sequence where the number of zero's (sic) increased, and would also have allowed the class to discuss the place value aspects of numbers with decimal points.

Feed it back to her. As a recently escaped teacher I would not have liked it but would have to have taken it on the chin! As I am/was also a bit brave, I would have used your email/info to open the next lesson...