[Closed] How many 10s in 868?

Crap!!

8 hundreds 6 tens 8 units

guess it depends on how the question is asked tho

Reminds me of the film Little Man Tate, when the eponymous character gets asked "which of the following numbers are divisible by 7?" and he replies - quite correctly - "all of them". The question is pitched and asked for a given audience, which means the answer might be nonsense to the "wrong" audience.

[i]8 hundreds 6 tens 8 units[/i]

But there are 80 10s in 8 hundreds..

86.8 is the answer I'd have given

6 is just some made up hippy bullshit

But there are 80 10s in 8 hundreds..

I was taught hundreds/tens/units at primary school, from the thread I assume it wasn't universal.

This is my point - especially in mathematics, you have to phrase questions properly, you should have to second-guess what the questioner was getting at. I would have said 86.8 too.

In the second example, the correct answer is apparently 10. Which again I can see how they get that, but it's a nonsense question.

It could also be 86 tens and 8 singles.

But in the context of teaching hundreds, tens and units, 6 is perfectly correct. Don't call it rubbish when you don't know the context.

IIRC hundreds, tens and units was taught before division. 86 or 86.8 is the answer to a division question, which presumably doesn't exist for these kids.

So if 868 were written in Hex (364) then that answer suggests it would have 6 sixteens but no 10s, whereas in decimal it has 6 tens and no 16s? But the number itself remains divisible by both 10 and 16 in exactly the same way regardless of how it's expressed. That's gotta confuse some kids.

or try writing it properly
eight hundred and sixty eight (aka eight hundreds, six tens and eight)

you wouldn't say
eighty sixty eight
or
eighty six tens and eight
would you?

86.8 is the answer to "what is 868 divided by ten?"

86 or 86.8 is the answer to a division question, which presumably doesn't exist for these kids.

It's mathematics - the correct answer shouldn't be different depending on the assumed knowledge of the student.

Some people would say eight sixty eight. A lot of people say things like 'twenty-six hundred' instead of 'two thousand six hundred' too.

Or it could be six gross and a third of a dozen.

It's mathematics - the correct answer shouldn't be different depending on the assumed knowledge of the student.

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.

A lot of people say things like

Which are nonsense without brackets.

don't most math science degrees begin with forget everything you've learned so far none of it is that simple.

I remember in my third year we finally proved that 1+1 = 2 😉 (first you need to define what zero is, then what 1 is and how your set of integers is constructed from that, then what + means and then you can get to the proof.)

doesn't make them right tho does it

I think technically, in English, it does 🙂

I remember a brilliantly phrased question from when I was at University. It read "Write down what you know about <subject>" I answered "Nothing". I reckon I should have got 100% for that answer.....!

Which are nonsense without brackets

No they're not. Maths operations have a specific order so even without brackets you know which parts to calculate first. Brackets are part of that specific order but aren't a necessity for the example you posted.

Look up BODMAS.

[EDIT - beaten to it by D0NK]

How many tens in 868?
At least three.

DrP

I had this with Jr a few years ago. It ties in with the methodology they are being taught for multiplication/division known as 'chunking'.

8 hundreds 6 tens 8 units

That's how I was taught at junior school. It's not a mathematics question, it's a numeracy question. It's part of teaching kids the significance of columns in numbers. (I remember at the time, one kid who would write two hundred and thirty seven as 200307...)

OPs question is only confusing because it is missing the context:

e.g. it is a test about "Place Values" not division.

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

In the second example, the correct answer is apparently 10. Which again I can see how they get that, but it's a nonsense question.

?? 5 surely?

1.5 is 1 unit and 5 tenths.

But the number itself remains divisible by both 10 and 16 in exactly the same way regardless of how it's expressed. That's gotta confuse some kids.

By the time they move on to bases other than decimal, they'll have - no, they'll [i]need[/i] - a firm grasp of what the columns mean.

1.5 is 1 unit and 5 tenths.

The logic, apparently, is that if you divide 1.5 into 10ths, there are 10 10ths in 1.5.

Basically, the correct answer to "How many 10ths are there in xxxx" is always 10.

And yes, I can see where they're going with place values, but they're still assuming the knowledge level of the pupil - my 3-year-old can grasp place value.

I had this with Jr a few years ago. It ties in with the methodology they are being taught for multiplication/division known as 'chunking'.

My daughter's learning long division at the moment, and she uses a really weird method to do it, nothing like how I learnt it... I just go along with her, I really don't want to confuse her by doing it a different way.

I get the feeling a lot of people on this thread haven't realised that maths teaching has moved on since they were kids! (Or that it can be taught in different ways).

[i]It's not a mathematics question, it's a numeracy question.[/i]

this the teaching of maths is very structured now.

If your child is still being taught about 100's, 10's and units then they won't expected to be in a position to also do the long division necessary to work out it's 86.8 10's.

If you try and get your child to do the 86.8 thing before they've firmly grasped place when working out tens and units you may cause problems.

If you have concerns I'd talk to the teacher about how the curriculum is being taught in your child's school.

I have some knowledge about English teaching of maths but not sure what differs in Scotland.

Most people don't remember how they were taught maths - I suspect we've all been through this process.

[edit] seen your most recent post - talk to them - they shoudl be differentiating work and have a specific learnign objective for each pupil in every lesson.

The logic, apparently, is that if you divide 1.5 into 10ths, there are 10 10ths in 1.5.

Eh???????

If it is [i]actually[/i] meant to be a division then surely there are 15 tenths in 1.5?

i.e. it could be written as the fraction 15/10 or as the words "fifteen tenths"

But if that question is from the same test as the first one then it is using the same language so [i]should[/i] also be referring to place value and the answer [i]should[/i] be 5.

The logic, apparently, is that if you divide 1.5 into 10ths, there are 10 10ths in 1.5.

Basically, the correct answer to "How many 10ths are there in xxxx" is always 10.

That is really crap. The how many tens thing I could accept but this?

By the time they move on to bases other than decimal, they'll have - no, they'll need - a firm grasp of what the columns mean.

Yep! Which is why it irks me that people teach kids to count from one to ten. We should teach them to count the units: ZERO to nine. Would save a lot of confusion IMO

The logic, apparently, is that if you divide 1.5 into 10ths, there are 10 10ths in 1.5.

Basically, the correct answer to "How many 10ths are there in xxxx" is always 10.

It really isn't. I think you must be mistaken, there's no logic whatsoever that would make that correct.

We should teach them to count the units: ZERO to nine. Would save a lot of confusion IMO

PS. I also presumed using place values the answer to the 1.5 tenths question was 5, you sure it's 10?

It really isn't. I think you must be mistaken, there's no logic whatsoever that would make that correct.

The full discussion is over on Mumsnet apparently - I just got it second-hand from the missus.

But I can see what the questioner is getting at. If you cut a cake into 10ths, it has 10 10ths. So if you asked "How many 10ths are there in a cake?" The answer would be 10. Substitute 1.5 for cake.

But it's a trick question really - like what's the difference between one quarter of a million dollars and one-quarter of a million dollars?

(The former is 25 cents, the latter is $250,000. Or maybe it's the other way around)

I would have guessed that dad got kid's homework wrong.

It is a method of teaching. It is not 'maths' the way a fully grown man would possibly understand it. Most people probably learned about numbers this way but have forgotten that this was a formative step en route to doing maths - it isn't maths, but it helps to teach it.

we also count on fingers, holding up your left thumb and saying "zero" is even more confusing shirley?

"zero" is "no fingers."

But I can see what the questioner is getting at. If you cut a cake into 10ths, it has 10 10ths. So if you asked "How many 10ths are there in a cake?" The answer would be 10. Substitute 1.5 for cake.

Yeah, but then you'd start with 1.5 cakes, so you'd have fifteen tenths.

And it's wrong anyway in the context of the first example, you've moved the goalposts. The first question is asking about units columns, the second (as you explain it) is a division question. Both are valid answers (ie, 5 or 15), but you can't just follow a units question with a mathematical division question without context, that's the sort of wooly unsolvable nonsense that ends up on Facebook. In the context of the first question, the answer to the second is "5," end of.

I'll say it again. 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."

Orbital mechanics (aka dead hard sums aka maths) allows us to plan the landing of a probe on a comet a bazillion miles away and works because maths is well-defined and not open to interpretation. Everything else is just bollocks.

But aswell as just reeling off the numbers 1 - 10 we also count on fingers, holding up your left thumb and saying "zero" is even more confusing shirley?

Just start with no fingers when you say zero.

(I'm doing this with my two kids because personally I think holding off on the concept of zero as some kind of "special thing" is anachronistic. Kids understand the concept of "none" - it's not hard).

Substitute 1.5 for cake.

Yeah.. but.. that only works because you have chose to substitute 1.5 (cakes) for 1 (cake).

You can't hold up one and half cakes and say you have one cake.

It's like saying "How many 427 sheep do I have in that field?"
"That's right I have one 427 sheep."

Edit: Cougar is clearly on my wavelength and [s]has less work to do[/s] [i]is a faster typist[/i]. 😉

"zero" is "no fingers."

0-9 may make sense for properly counting Tens, just not sure how it would work - I guess I'm probably tied to the decimal = count on [s]fingers[/s] digits concept.

D0NK: you can put your thumb up to count ten, but then, importantly, LEAVE it up as you count up to 19 😀

(Oh and make it your left thumb, tens go on the left!)

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 🙂

Did cross my mind but what about after 19?

Nobody likes a clever dick.

Ultimately I think it is flawed either way D0NK (really having ten fingers means that we [i]should[/i] theoretically use a base 11 counting system 😀 )

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)

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"?

The full discussion is over on Mumsnet apparently

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

[i]One thousand posts[/i] 😯