Simple maths question...
Discussion
As I suspected!
It’s not a trick question, but parentheses are not required.
8 - 5 + 1 = 4
Why? Although Addition appears before Subtraction in the BODMAS mnemonic, addition and subtraction carry equal operational priority so must be performed in the order they are written when reading from left to right.
I’ll be discussing this with my 9yo son’s maths teacher when term restarts...
It’s not a trick question, but parentheses are not required.
8 - 5 + 1 = 4
Why? Although Addition appears before Subtraction in the BODMAS mnemonic, addition and subtraction carry equal operational priority so must be performed in the order they are written when reading from left to right.
I’ll be discussing this with my 9yo son’s maths teacher when term restarts...
BODMAS doesn't need to be applied here. You have 9 in the positive column and 5 in the negative. Answer is 4 no matter which order you work it out in.
You can't separate the 5 from the minus in front of it, so even if you work out the second half first, it must be -5+1, which = -4. That would leave 8-4, which is still 4.
If you add brackets as in 8-(5+1), you change the question. The 5 is now +5, not -5, and the 5 and the one are now both multiplied by -1, making them effectively both negative. i.e. 8-(6)
The answer, without brackets, is 4. The question, with brackets, is a different question with different numbers in it.
You can't separate the 5 from the minus in front of it, so even if you work out the second half first, it must be -5+1, which = -4. That would leave 8-4, which is still 4.
If you add brackets as in 8-(5+1), you change the question. The 5 is now +5, not -5, and the 5 and the one are now both multiplied by -1, making them effectively both negative. i.e. 8-(6)
The answer, without brackets, is 4. The question, with brackets, is a different question with different numbers in it.
Michaelbailey said:
I don't know why the schools insist on this teaching? It was the same when I was in school many moons ago
Beyond belief isn't it.
Kids leaving school with the ability to calculate something in a way which, in the real world, is useless. Yet they've had no guidance on working out the things that are likely to matter to them, such as which mortgage works out cheaper over the term etc....
The Ferret said:
Beyond belief isn't it.
Kids leaving school with the ability to calculate something in a way which, in the real world, is useless. Yet they've had no guidance on working out the things that are likely to matter to them, such as which mortgage works out cheaper over the term etc....
You are saying that kids shouldn't be taught the basics of maths (at a young age), but should be given guidance on how to actually applied mathematics (presumably at an older age) without it?
BODMAS/BIDMAS might seem redundant but I'm pretty sure there's a good reason its still there. Its just that most computers etc have got it programmed in to them already, so that when you come to work out your mortgage (or similar) it takes it all into account for you..
The Ferret said:
Michaelbailey said:
I don't know why the schools insist on this teaching? It was the same when I was in school many moons ago
Beyond belief isn't it.
Kids leaving school with the ability to calculate something in a way which, in the real world, is useless. Yet they've had no guidance on working out the things that are likely to matter to them, such as which mortgage works out cheaper over the term etc....
Mammasaid said:
Not sure if serious....
I think the points been missed. I assume Ferret was referring to addition before subtraction when as has been said before isn't correct despite bodmas. obviously teach the brackets and overs etc but not a dumb technicality which would always be shown with brackets. As the OP said being marked wrong on homework for it. I remember my history teacher once saying to me when starting learning about WW2, "this isn't strictly accurate however this is what we will use as being true for GCSE, if you take history further itll be different". Similar story with chemistry although that was more of a simplification at GCSE rather than what they actually teach you at A level and uniV8covin said:
I had never heard of Bodmas until last year when someone put up something similar on Facebook.
I'm 55,got an o'level in maths at 15 at the best school in the area education wise.
We were taught left to right,the trouble is calculators use Bodmas .
The world can be a confusing place
But in that case you'd have got, for example I'm 55,got an o'level in maths at 15 at the best school in the area education wise.
We were taught left to right,the trouble is calculators use Bodmas .
The world can be a confusing place
4 x5 +2 = 22
and
2 +4 x5 = 30
and only 50% in your maths test.
Michaelbailey said:
Mammasaid said:
Not sure if serious....
I think the points been missed. I assume Ferret was referring to addition before subtraction when as has been said before isn't correct despite bodmas. obviously teach the brackets and overs etc but not a dumb technicality which would always be shown with brackets. As the OP said being marked wrong on homework for it. I remember my history teacher once saying to me when starting learning about WW2, "this isn't strictly accurate however this is what we will use as being true for GCSE, if you take history further itll be different". Similar story with chemistry although that was more of a simplification at GCSE rather than what they actually teach you at A level and uniThere has to be rules of showing and then calculating arithmetic that everyone adheres to, otherwise we'd still all be eating woolly Mammoth around a camp fire.
And more people will be using simple arithmetic like this in their day to day lives than working out compound interest.
The Ferret said:
Beyond belief isn't it.
Kids leaving school with the ability to calculate something in a way which, in the real world, is useless. Yet they've had no guidance on working out the things that are likely to matter to them, such as which mortgage works out cheaper over the term etc....
Mammasaid said:
It was more the 'in the real world it's useless' remark.
There has to be rules of showing and then calculating arithmetic that everyone adheres to, otherwise we'd still all be eating woolly Mammoth around a camp fire.
And more people will be using simple arithmetic like this in their day to day lives than working out compound interest.
I see. I think ultimately maths is almost redundant to some people post school. There has to be rules of showing and then calculating arithmetic that everyone adheres to, otherwise we'd still all be eating woolly Mammoth around a camp fire.
And more people will be using simple arithmetic like this in their day to day lives than working out compound interest.
And to the comment about kids wont need to work out mortgages anymore, whilst quite amusing im proud to say i got my house/mortgage aged 20 (i am 22 now) There is still hope!
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