Maths Disagreement

[TulaOfDarkWater]

One person thinks the answer is 165 and the other thinks 67, who is right?

YABU - 165
YANBU - 67

Or what’s the answer if both are wrong?

@daisypond

I get 35. The shapes, bananas, clocks and calculations are different on last row: Last row banana =3 Last row clock = 2 Last row shape = 10

2 + 3 + ( 3 x 10) = 35

Last row shape = 11

Is this still dragging on? The answer's 38 for the reason stated multiple times. The algebra has been really interesting - I was taught that so poorly at school I never really got my head round it properly.

I didn’t have a happy experience with maths in school. I didn’t like my teacher and she didn’t like me, which was fair enough as I didn’t listen and messed about a lot. I spent a fair bit of time standing in the corridor, having been sent out, so I probably missed a lot. Nonetheless, I managed to get a B at GCSE.

As an adult, I began to see that I had a lot of gaps in my knowledge. I made a conscious effort to improve after I had my children, so that I could better help them with their homework.

I was unaware of BODMAS until I came across it on MN ten years ago or so. I imagine I was taught it but my lack of interest/effort, possibly coupled with some poor teaching meant it hadn’t sunk in at all. I’m glad I now understand it and I enjoy maths puzzles and problems a lot more now.

When someone posted 40 / 0.5 earlier in the thread, I felt that old, familiar panic as I realised I had no idea what the answer was and no idea how to approach it. I couldn’t feel any instinct for it at all. Once posters used the cake explanation, I could instantly see how simple it was. I hope I’ll remember those cakes the next time I come across such a question! Some of us just need very physical representations of these concepts.

I got the answer 38 to the original problem though

Hi, @waterlego -

Your maths journey is very interesting. Your children are lucky that you cared enough to learn maths for them, and you’re obviously capable. It is interesting to me that you know what you need, such as the physical representation @ThumbWitchesAbroad gave with the cake for the division problem. So glad you like maths puzzles more now!

Now I’m craving cake again :)

[quote PugInTheHouse]@bruffin I am slightly obsessed my maths stuff. There was a great post on FB recently where people were discussing the answer to 40÷0.5[/quote]
I assume they were debating 1 + 1 = 2, in the decimal system, too! How can you discuss such a basic fact as 40/0.5 = 80?

Thanks @poetryandwine, what a nice message! I really REALLY didn’t want to be one of those people (usually women, I have to say) who say ‘I’m terrible at maths!’ with a giggle, and wear it as some sort of badge of honour or something to laugh about. It’s often been pointed out on MN that people don’t really talk about reading and writing in that way; it seems to be something that is reserved only for maths.

I didn’t want my kids to hear that from me, especially my daughter. Interestingly, despite my best efforts to be positive and enthusiastic about the subject, she also suffers from the same sort of ‘maths panic’ that I experience. She does really well in the lessons, but the exam situation induces the fear; her mind goes blank and she doubts herself (only for maths though, she can cope with all the other exams!)

She is now in her GCSE year, is in one of the top groups for Maths and is predicted to do well in the exams. She certainly enjoys the subject more than I did at school and wants to do well at it. If she can master some coping strategies for the exam anxiety, I think she’ll do well.

And I want cake too. Preferably 40 / 0.5 of them.

Hi, JudgeJ -

I did not see the FB post, but one answer to your question is that I have observed even highly numerate people to construct incorrect story problems to model this problem. Why they do this is a very interesting question in itself

Edit: meant to tag @JudgeJ in the post above

@waterlego

Thanks *@poetryandwine*, what a nice message! I really REALLY didn’t want to be one of those people (usually women, I have to say) who say ‘I’m terrible at maths!’ with a giggle, and wear it as some sort of badge of honour or something to laugh about. It’s often been pointed out on MN that people don’t really talk about reading and writing in that way; it seems to be something that is reserved only for maths.

I didn’t want my kids to hear that from me, especially my daughter. Interestingly, despite my best efforts to be positive and enthusiastic about the subject, she also suffers from the same sort of ‘maths panic’ that I experience. She does really well in the lessons, but the exam situation induces the fear; her mind goes blank and she doubts herself (only for maths though, she can cope with all the other exams!)

She is now in her GCSE year, is in one of the top groups for Maths and is predicted to do well in the exams. She certainly enjoys the subject more than I did at school and wants to do well at it. If she can master some coping strategies for the exam anxiety, I think she’ll do well.

OK maths exam strategy from my maths teacher in the early 1980s.

Hope you get a hard paper, because then other people will waste time panicking.

Just look through the paper for something easy and start with that.

Good advice @sashh! I’ll tell her that.

JudgeJ I assume they were debating 1 + 1 = 2, in the decimal system, too!

Are you sure 1+1=2?

DO NOT READ THIS IF YOU DON'T ENJOY MATHS

Suppose a = b
Then multiplying by a gives a^2 = ab

And then subtracting b squared gives a2 - b2 = ab - b^2
Factorising (a-b)(a+b) = b(a-b)
Now divide by the common factor leaves a+b = b

So if a = 1 then as a=b b= 1 as well, so substituting in gives 2=1.

For avoidance of doubt, @TeenPlusCat has given us a nice maths puzzle just above. She isn’t seriously suggesting that 2=1!

@TeenPlusCat

JudgeJ I assume they were debating 1 + 1 = 2, in the decimal system, too!

Are you sure 1+1=2?

DO NOT READ THIS IF YOU DON'T ENJOY MATHS

Suppose a = b
Then multiplying by a gives a^2 = ab

And then subtracting b squared gives a2 - b2 = ab - b^2
Factorising (a-b)(a+b) = b(a-b)
Now divide by the common factor leaves a+b = b

So if a = 1 then as a=b b= 1 as well, so substituting in gives 2=1.

Ha!

That's cheating.

If you do the maths with the numbers, the last equations come out as 0 = 0, so yes, 0 does = 0, but you can't substitute the numbers back in at the end!

Thus:
Suppose a = b

1= 1

Then multiplying by a gives a^2 = ab

1^2 is 1, ab = 1x1, so 1 = 1

And then subtracting b squared gives a2 - b2 = ab - b^2
12 - 12 = 1x1 - 1^2 --> 0 = 0

Factorising (a-b)(a+b) = b(a-b)
(1 - 1)(1 + 1) = 1 (1 - 1) --> 0 x 2 = 1 x 0 therefore 0 = 0

Now divide by the common factor leaves a+b = b
The common factor at this point is a-b, which = 1-1, which is 0. You divide anything by 0 and it equals infinity - so you could have infinity = infinity, but we don't need to do this if we're working with numbers because we already know that 0 = 0

This is a very clever algebraic ploy but it doesn't work with real numbers. Nice one though! Does it have an actual application?

This is a very clever algebraic ploy but it doesn't work with real numbers. Nice one though! Does it have an actual application?

Not that I am aware of, I was just teasing/testing people really

Yes, of course!

@TeenPlusCat nope you’re dividing by zero