help with Yr5 decimals please

[arcticwind]

My dd is really struggling with decimals. She has a different teacher this year who is doing things a different way from how she were taught last year, but because this teacher taught some of the year group last year she thinks they all know her methods.

Dd is not at all confident in maths and has to work really hard to understand things and being told off for not rememebring what she hasd not actually being taught is not helping!

I would like to help her understand the whiole concept, so please if anyone knows any websites etc to help I would be very grateful.

I am not confident that her teacher will listen to me and not carry on confusing dd with her alternative (and TBH barking) method.

Thanks

i'm getting \link{http://www.letterbox.co.uk/27809-11545XXX/maths-cubes\these sets} for my son, they look as though they could make the whole concept more understandable! (they do decimals and percentages but not shown there)

Some of these resources, particularly the powerpoints may be useful.

This one for interactive games.

BBC is good too. :)

If you go to the Teachers' TV website there is a series of programmes called Maths Mansion.

I can't remember the exact episode, but there is one that reinforces understanding of decimals - it uses a character called Deci-Mole.

It helps if they think of decimals in terms of money
e.g 1.25 = £1.25; say it in terms of One whole pound and 25 pee

No good once they start looking at equiv fractions but will help her feel more confident to begin with.

how is the new teacher approaching it? What is her method?

I love Maths mansion! I played it regularly for my year 4 children, who were top group maths. It really is excellent and Chris Jarvis is the bloke on it, which surprised me when I had a little one of my own and was on cbeebies.
The worms might help.

Can your DD do the sums without the decimal point? Quite often this is the starting point of learning how to do the sums, and then decimal points come in later. If she cant do the sums, then decimal points will confuse her.

Is she struggling with addition/subtraction/ multiplication or division with decimal points?

On Maths Whizz they teach you to do the sum without the point and then add it into the answer (certainly on one game I viewed)

It would be good if you could explain what your DD has told you and then someone on here would probably understand what/how she is being taught

happywheezer - the children had to point out to me that 'Sad Man' was the same person as the main presenter

Thanks all

The main issue is multiplying / dividing by factors of 10 (so 10, 100, 1000 etc).

The teacher is telling her to 'move everything' to the left or right (depending on whether it is multiplication or division) but dd thinks you have to move the decimal point and sticks the zero in a very odd place so 31.5 x 10 becomes 310.5 !!!

She is fine with normal mulitplication or division y 10 - adds / subtracts her zeros - but I think does not really understand the whole concept of where decimals come from, and 'leading' zeros

I will check out those websites, many thanks

arcticwind - it sounds as if the problem stems from the fact that she thinks (or has been taught) that to multiply by 10 you add a zero.

To multiply any number by 10 you need to understand that you are moving the digits on place to the left (obviously adjusting the rule for 100/1000 and division).
If she thinks you just add a zero she will struggle with decimals.

It's one of my biggest bugbears with Y5 and 6 (I had to ask the Y2 teacher to stop saying 'add a zero' as it causes huge problems later on)

I've just been covering this with my class and had to reteach basic multiplication by 10/100/1000 in order for them to multiply decimals

arctic, my DD is in Year 4 and that is how they are learning it too. DD's teacher does the "moving everything to the left/right" step by step too, but apparently he stresses that the decimal point stays still. So,

31.5 x 10
= 315.0
(in the second line each digit is moved one place to the left, leaving the decimal point as it is)

and say,

31.5 x 100
= 315.0 x 10
=3150.0

and similarly,

31.5 / 10
= 3.15
(by moving each digit to the left, leaving the decimal point in place)

or,
31.5 / 100
= 3.15 x 10
= 0.315

It is quite confusing as you tend to think of multiplication by 10 as moving the decimal place one point to the right (which is of course what has happened by moving the digits left).

Grrr, the formatting has gone so it makes no sense at all . The decimal points are all supposed to be aligned .

lol thanks megapixels - I get the idea :)

Glad I am not the only one who is confused - what is wrong with the tried and tested methods!!!

Pantryboy you are spot on - she really does not have a mathematical brain so takes things literally. I, on the other hand, do, so find it incredibly hard to help her ...

not to mention that the way they teach is different so I run the risk of confusing her even more

sigh ...

When we started this topic one of my year six pupils (I taught him last year as well) said 'oh, this is when you make us do 'the decimal point never moves' activity'

I was delighted, as I pointed out to him the fact that he had remembered meant it must work.

Regarding the last two posts, I'd really like to understand why the posters feel that moving the decimal point is wrong. I understand that it is technically correct to think in these terms but the concept of moving the decimal point is a tried and tested simple method that works and requires far less cognitive processing to implement.

I was watching my daughter struggle with these exercises until I suggested she ignore her teacher's edict of not moving the decimal point. 30 seconds later she was getting 100% on every exercise...

Why is it 'bad practice' and 'chaos'?..

I make some practical apparatus for the children I tutor. I print out some smallish 10 by 10 square grids and stick them onto craft foam sheets for easy handling. Then cut them out so they are solid colour foam on one side and a 10 by 10 grid on the other.

I explain to the children that these are "whole squares" and do some simple sums (3 + 2 etc) to demonstrate.

Then I explain that the decimal point means "Stop working with whole squares and start cutting them into bits". and because we have a decimal system we start by cutting them into 10 bits. I give them scissors and ask them to cut a square into 10 strips following the grid lines. Explain that these are called tenths because 10 of them make up one whole one.

Then do similar splitting a tenths into ten by cutting along grid lines. Explain these are called hundredths because 100 of them make up a whole square. They can check this by looking at grid side on "whole squares".

I show how these are recorded by digits after the decimal points.

Then I get them to do lots of practical sums manipulating this apparatus. In practice I'd probably do lots of work with tenths until they were confident before introducing hundredths.

The effect of multiplying by 10 can be seen visually.

Eg 0.3 x 10 =

Get them to put 3 of the tenth sticks on table and confirm this represents 0.3 or three tenths. Wave a tenth stick at them and say "if I multiply this by ten, what do I get?" Answer "one of the whole squares" (they have already made the tenths sticks by cutting a whole square into 10 strips so should get this easily)
Do this for each of the tenth sticks in turn. You will end up with 3 whole squares. So you can show that 0.3 x 10 = 3.

I do this lots of times and introduce hundredths as well ( when you multiply one of the little hundredth squares by 10 you get a tenth stick - they've done this in reverse by cutting so they usually get this too)

Once they've done loads with the apparatus, they usually "get the pattern" and can do the sums without the equipment. I then extend to dividing by 10 and multiply/divide by 100.

I extend my apparatus by taking ten whole squares and skewering them on a piece of wooden kebab stick ( glue a bead on each end to stop coming off) explaining that it means we can count tens of whole squares easily.

This equipment is great for showing them the difference between 10 and a tenth and that 0.7 + 0.5 does not equal 0.12. (If you do the sum with actual tenth sticks you can see that you have enough to make one whole square plus 2 tenths ie 1.2) you can also see easily that 3 tenths = 30 hundredths etc

Once they are really confident I introduce thousandths by asking them to imagine cutting a hundredth little square into 10 bits ( too small to actually do this!) and we pretend to manipulate tiny thousandth pieces!

This sounds complicated - a lot easier to show rather than explain in words but I hope it makes sense!

I think the advantage of this over using things like coins is that the actual size/shape of the pieces shows their relationship to each other and the fact that you can get the child to actually cut up the pieces themselves.