How many 10s in 868?

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  • How many 10s in 868?
  • Premier Icon D0NK
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    Did cross my mind but what about after 19?
    sorry not trying to shoot it down just want to get my head around it
    Would also teaching kids binary help with this sort of thing aswell? stop thinking purely in decimal and concentrate on the units/values? or just confuse matters further? the option to count upto a 1023 on your hands has geek appeal πŸ™‚

    Premier Icon Cougar
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    Did cross my mind but what about after 19?

    Nobody likes a clever dick.

    Premier Icon GrahamS
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    Ultimately I think it is flawed either way D0NK (really having ten fingers means that we should theoretically use a base 11 counting system πŸ˜€ )

    I think the important thing is to get kids used to the idea of zero as the starting number, rather than introducing it as some magically thing that appears as “a placeholder” at ten – and then reintroducing it as a proper number when they get to number lines etc.

    (Note: I am not a teacher, just a parent. And a programmer)

    Premier Icon D0NK
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    I did see that coming cougar (fnar fnar) but thought no-one would be base (10) enough to say it

    graham fair enough. May start doing 0 1 2 3 4 5 6 7 8 9 *pause* ten start again! or something
    IMO it’s 10-19 that screw it up, especially 11 and 12, after that you’ve got proper sets twenty thirty etc, why do we have eleven instead of “onety one” or “oneteen”?

    SamB
    Member

    The full discussion is over on Mumsnet apparently

    http://www.mumsnet.com/Talk/_chat/a1988081-How-many-tenths-in-1-5

    One thousand posts 😯

    hora
    Member

    Eh. I must be thick as the answer is 86 (.8). How is the answer 6?

    Premier Icon GrahamS
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    hora: it’s not about division:

    See http://www.mathsisfun.com/place-value.html

    Premier Icon GrahamS
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    IMO it’s 10-19 that screw it up, especially 11 and 12, after that you’ve got proper sets twenty thirty etc, why do we have eleven instead of “onety one” or “oneteen”?

    A man after my own heart πŸ˜€

    It’s amazing how many of these universally-accepted-yet-weird things you notice when you have kids and they start asking “Why?” πŸ˜€

    English is just as fickle: e.g. drink, drunk, drank.. wtf?

    Really odd when I thunk about it properly.

    I was Mr thicky McThick at Maths but having read the posts even I get it. OP it’s not hard, really it isnt.

    Premier Icon Cougar
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    After looking at the first page of Mumsnet there I see where they were going with this now.

    10. There are always 10 tenths of a whole whether the whole be 15 or 370. Each tenth is 1.5.

    The “logic” here is you have “something”, you divide it by ten, how many parts do you have? Ten!

    It’s flawed logic though. If your “whole” is six oranges, you’d end up with ten tenths of six oranges, which is nonsensical.

    The thread says it’s a badly worded question. It’s not, it’s just out of context. The kid learns about units all day – hundreds, tens, units, tenths, hundredths – then comes home and goes “mum, how many tenths are there in 1.5?”, mum then posts to Mumsnet and chaos ensues because they’ve not been given sufficient information to solve the question in the manner being tested for.

    Premier Icon andytherocketeer
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    Orbital mechanics (aka dead hard sums aka maths) allows us to plan the landing of a probe on a comet a bazillion miles away

    well that’s sort of my job, and my answer is 6

    Premier Icon D0NK
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    if you have difficulty with hundreds tens and units don’t look at leaf diagrams

    Premier Icon Cougar
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    And the truth is revealed.

    That question is from a different sheet.

    I was right about moving goalposts. They’re two different examples from two different question sheets (potentially) testing two different things. No wonder it ran to a thousand posts.

    Premier Icon GrahamS
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    Mumsnet… It’s flawed logic though

    Quite!

    (Maybe that could be their tagline?)

    jon1973
    Member

    Eh. I must be thick as the answer is 86 (.8). How is the answer 6?

    868

    8 ‘hundreds’
    6 ‘tens’
    8 ‘units’

    hora
    Member

    DONK I just tried

    fasthaggis
    Member

    mum Hora then posts to Mumsnet and chaos ensues

    mogrim
    Member

    if you have difficulty with hundreds tens and units don’t look at leaf diagrams

    Easy enough to understand, I just wonder why you would want to set your data out like that?

    Premier Icon GrahamS
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    It’s a histogram for people without Excel. πŸ™‚

    (and better than a histogram in one respect, as it leaves the original data intact).

    Premier Icon Cougar
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    That Mumsnet page just keeps on giving. “I have a maths degree!” – yes, but this is Key Stage 2. Your average junior school kid isn’t going to be doing differential calculus, they’re going to be learning what it means when you move a digit one to the left.

    Premier Icon GrahamS
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    “I have a maths degree!”

    Like the pilots and aircraft engineers that show up on the airplane/conveyor belt thread.. and get it wrong. πŸ˜€

    Premier Icon wwaswas
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    My wife has a Master Degree in how the under 7’s learn mathematical concepts.

    It’s sometimes quite counter-intuitive for those of us who already understand it.

    Premier Icon Cougar
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    Gods, someone’s talking about Base 1 now. WTF is base 1? A numerical system where a digit can have one value?

    “Count after me, children:
    1,
    11,
    111,
    1111,
    …”

    “Miss, what’s 1 minus 1?”

    “Don’t be clever, Henry.”

    Premier Icon miketually
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    Its like these questions that are posed in facebook which go along the lines of 1 x 2 – 3 + 4 x 6 = ??? Which are nonsense without brackets.

    Firstly:

    It’s like the questions which are posted on Facebook, which go along the lines of 1 x 2 – 3 + 4 x 6 = ? , which are nonsense without brackets.

    No brackets, not nonsense:
    1 x 2 – 3 + 4 x 6 = 2 – 3 + 24 = 23

    On the original question, division by ten and “how many tens?” on a place value exercise are very different.

    Premier Icon wwaswas
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    A numerical system where a digit can have one value?

    I’m all for base 0.

    mogrim
    Member

    It’s a histogram for people without Excel.

    My first thought was why bother doing it like that, when you could just use a spreadsheet πŸ™‚

    TBH, I think I’d rather my kids learned to use a spreadsheet than learning about leaf diagrams, seems more useful. Although I’m willing to admit I could be missing something, do these diagrams lead on to something more interesting?

    Premier Icon miketually
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    I’m a qualified primary school teacher, who now teaches GCSE maths and A level physics. Am I correct in thinking I’ll get annoyed if I look at the Mumsnet thead?

    jfletch
    Member

    Unless you’re dealing in something other than decimal there is no way while I’ve got a hole in my arse that the correct answer to “how many tenths are there in 1.5” is “10.”

    I think when teaching kids they just leave out a bit of context that we as grown ups need due to our extra knowledge of division. The question would be better phrased as…

    “How many tenths of 1.5 are there in 1.5?”

    That makes the answer obviously 10. They are trying to test that the puplil knows that “tenths” = spilt into ten lumps.

    A similar question could be…

    “How many eighths (of 763) are there in 763?” with the answer being 8.

    Its not intuative but then I’m not 8. I may have to take a course when my kids are old enough to go to school!

    Premier Icon miketually
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    I think I’d rather my kids learned to use a spreadsheet than learning about leaf diagrams

    It’s not one or the other.

    (Although, I’d never even heard of a stem and leaf plot until I taught it for the first time, and I’m still non-the-wiser on when they’d be used. They do make it easier to find the mode and median values when working by hand.)

    Premier Icon Cougar
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    No brackets, not nonsense:

    Again, it is a nonsensical without context. You’re correct according to operator precedence, but would primary school children be learning BODMAS?

    That’s the mistake some of the Mumsnet lot are making, all degrees and no common sense.

    Premier Icon miketually
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    would primary school children be learning BODMAS?

    Yes.

    Premier Icon Cougar
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    Fair enough then (-: It was actually a genuine question, you answered before I edited the post to say so.

    Premier Icon Cougar
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    “How many eighths (of 763) are there in 763?” with the answer being 8.

    I find it hard to believe that this is the sort of question that would be asked in a school maths lesson. A Christmas cracker, maybe.

    mogrim
    Member

    It’s not one or the other.

    (Although, I’d never even heard of a stem and leaf plot until I taught it for the first time, and I’m still non-the-wiser on when they’d be used. They do make it easier to find the mode and median values when working by hand.)

    I appreciate you could teach both, but I’m still thinking that leaf diagrams are a bit of a waste of time, and given that time is limited it would be better spent on learning how to get Excel to do the hard work for you. (With appropriate theory taught first of course, not just plugging the numbers in and getting the answer!)

    WackoAK
    Member

    ten tenths of six oranges

    BOOM!

    Premier Icon miketually
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    I teach stem and leaf diagrams because they’re on the exam, not because I think they’re useful πŸ™‚

    Premier Icon GrahamS
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    “How many tenths of 1.5 are there in 1.5?”

    That makes the answer obviously 10.

    No that makes it WAAAY less obvious.

    a “tenth of 1.5” is 0.15

    So “How many tenths of 1.5 are there in 1.5?” means “How many 0.15 are there in 1.5”

    They are trying to test that the puplil knows that “tenths” = spilt into ten lumps.

    They’re not. Mumsnet has it wrong.

    They are either testing division skills (possibly) or they are testing knowledge about place values (most likely).

    If they wanted to test splitting whole things into ten parts as the definition of “tenth” then the question would have been “What is a tenth of 1.5?”

    Premier Icon GrahamS
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    I appreciate you could teach both, but I’m still thinking that leaf diagrams are a bit of a waste of time, and given that time is limited it would be better spent on learning how to get Excel to do the hard work for you.

    Same argument as “Why teach kids to multiply or divide when in reality they’ll just use a calculator.”

    mogrim
    Member

    Same argument as “Why teach kids to multiply or divide when in reality they’ll just use a calculator.”

    Not sure it is, a leaf diagram seems to have little or no use in real life, beyond passing your GCSE maths exam.

    Premier Icon GrahamS
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    Whereas long division… πŸ˜‰

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