doing a maths night class, can any one in simple terms explain to me:

[dissle]

How to do percentages,
How to turn a fraction into a percentage and back?
How to do subtraction...yes really, i absolutely struggle and get a different answer each time i do them.

How to turn a fraction into a decimal number.

there HAS to be an easy way to do and remember these things.

yes you simplify a fraction until the "numerator" (the one at the top)
and the "denominator" (the one at the bottom) have no common factors
some rules to find common factors

1. first see if the top number goes into to
   bottom number 10/100, 2/16 etc

2. are they both even numbers - then they have a common factor of two

3. do the digits in the numbers add up to a number divisible by 3
   12 =>1+2 = 3
   15=>1+5 = 6
   72 => 7+2 = 9

4. if it is even and divisible by 3 it will be divisble by 6

5. if the number ends in 5 it is divisible by 5

6. if the number ends in a 0 it is divisible by 5 and 10

7. then remember back to your times tables

So my services as a presonal tutor are not reuqired then dissle?

I explained the borrowing from the next column up to DD2 as:
units = single sweets
tens = packet of ten single sweets all wrapped up.
So if you don't have enough single sweets, you borrow a packet form the next column, and unwrap teh packet to give you 10 single sweets. Add to what you already have and do the take-away.
Then just scale it up to a multipack of packets, a box of multi-packs, a case of boxes, aand so on. Always remembering that the single unit is an individual wrapped sweet, so that a multipack of ten packs is 100 single sweets, to keep the place value there (i.e. that 1 in the hundreds column is really 100).
And similarly with adding, you can wrap up ten individual sweets to make a pack, which goes in the next column as you can't have more than 9 sweets/packs/boxes in a column.

Hello can I come in here (need help) as was trying to help DS1 with homework. On the 468-376 example that MB gave, I would have (as taught at school) taken 6 from 8, and then because you can't take 7 from 6, I would add 1 to six making 16 minus 7, then added 1 on the column to the left (3) making 4-4 = 0. Same answer I know but how/why is this done differently now as finding it difficult to help him. Can you please provide the rules.
Thanks.

there is no right way to do these things, children have to learn them
so they get to understand how numbers work and the differences between units, 10s and 100s etcs.
but yours and MBs is the same but i think she might have made a typo [?]

You are quite right, I did make a type

It is hard to type the stuff out!

468
376-
--

first take 6 from 8= 2

You cab't take 7 from 6, becayuse 7 is bigger than 6.

You borrow one from the next column along, and make the 6, 16 (because the next column along is 10 time bigger, so 1 from there = 10 IYSWIM)

You can now take 7 from 16

Beause you borroed one you have to pay it back, and you put that on the bottom and add that on to the 3, which makes it a 4. 4-4=0

468
376-
1
-
092

Flowertop, your way is called equal addition and is the method half the population were taught. The other way "borrowing" is called decomposition and is the way the other half were taught. Both are right, but I know as a professional that parents find it hard to take on whichever method they did not know as a child. Depending on your child, it will either confuse him to learn your method, or help him!

Can I be cheeky and ask for a couple of examples/explanations for the decomposition way. If you could use zeros in the number you are taking away from that would be really helpful.
I was helping DS1 with h/work last night and getting into a right old paddy as he didn't understand me and I didn't understand him. This thread is a godsend - thank you so much dissle for highlighting it and everyone else for solving it!!

110- 20

110 *20-

You cant take 2 from 1, 2 is bigger than 1

so you borrow 1 from the hundreds column, which make the 1, 11.

Take 2 from 11= 9

you then have to pay the 1 back

110 *20- 1

090

if you can get dcs do not both ways then you will know they really understand it!

702 - 381

You start with the units: 2-1=1

You move to the tens: 0-8= you can't do this. Therefore go to the hundreds column and borrow one hundred (from the 7) So you are taking one from there, leaving 6 there, and adding one hundred to your original 0 tens (so you will now have 10 tens) Now your tens column reads 10-8=2

Now move to the hundreds column. It now reads 6-3=3

Therefor the answer is 321

sorry that should be "dcs to do"
another example

1007-304

1007
304
-

7-4 = 3
0-0=0
0-3+problem
so you borrow from the next column to get 10-3=7
pay back and you get 1-1=0

this gives 703

that is one of the reasons for the night class. My ds has just started school, i need and want to be able to help and participate with his work.

am useless with no maths qualification at all.
Think i have dyscalclia, however when it explained like chippy girl ans martian...i get it and it works for me.

just have to remember it now.

thanks dumbledore...that is how i do it, i just needed to go back to basics, think i had got myself confused. (easily done)

There are 2 methods of subtraction here - the one where you 'borrow' 10 and then pay it back (martianbishop etc), and the one where you 'move' the ten and don't pay it back (dumbledoresgirl). I was taught the second method. I was shown a third method a few weeks ago and it confused me even more!

For another method there is the addition one where it focuses on subtraction being the difference between 2 numbers - so for 468-376 you start with 376 ...

376+4=380 380+20=400 400+60=460 460+8=468

Then you add up all the bits you added on

4+20+60+8 = 92

so

468-376=92

Sorry if this has confused you but it is a method that is widely taught in schools and I have been asked more than once to explain it to parents.

Sorry - those numbers shouldn't all be in bold (must preview!)

okay teachers prof and amateur who wants to explain long division?

not long division, but a very funny explanation of subtraction

long division is dividing one digit at a time

eg 12 divided by 3 (no sign for that !)
look at the 1 - you can't divide that by 3 - so you then make it 12 - can you divide that by 3 ? yes - so the answer is 4.

123 divided by 3 - same as before - can't divide the 1, so divide the 12 - giving 4, then go to the 3 - divide that - giving 1 - so the answer should be 41. To check multiply 41 by 3 - you should get 123.

The trick is to keep the numbers in the right place in the sequence - if you write it out as a series of sub sums then you can move across and down the page as you go (not sure if they still teach it this way - my DS hasn't got to long division yet !).

I was never taught to do long division but I can't remember how I was taught to do this kind of sum!