Multiplying numbers?

Glaucus · 14 Jun 2007 at 21:25

I know you can do the grid method, but is there any easier way to do it in your head?

I know this is simple stuff, but hey..

and |I know the easy way for 11.

yhack · 14 Jun 2007 at 21:26

If it's x20 then do x10 then x2 and it's easier, stuff like that makes it a lot faster to work stuff out for me.

Glaucus · 14 Jun 2007 at 21:27

yhack said:
If it's x20 then do x10 then x2 and it's easier, stuff like that makes it a lot faster to work stuff out for me.

yeh I was thinking more in the lines of 12, 13,14,15 ect.

yhack · 14 Jun 2007 at 21:29

AcidHell2 said:
yeh I was thinking more in the lines of 12, 13,14,15 ect.

Sorry, I seemed to miss that part of the first post. It's like it wasn't there.

Angus-Higgins · 14 Jun 2007 at 21:29

Just split it up into (10x + 5x) for 15x. That is what I would do.

Angus Higgins

Jokester · 14 Jun 2007 at 21:30

AcidHell2 said:
yeh I was thinking more in the lines of 12, 13,14,15 ect.

Say 13 x 14, I would do 10 x 14 then add 3 x 14.

Jokester

Glaucus · 14 Jun 2007 at 21:30

yhack said:
Sorry, I seemed to miss that part of the first post. It's like it wasn't there.

he-he, I did forget to put it in, I wasn't having a go.

Glaucus · 14 Jun 2007 at 21:32

Jokester said:
Say 13 x 14, I would do 10 x 14 then add 3 x 14.

Jokester

oh yeah baby, why didn't I think of that.
thanks

..

I havent had to do simple maths for a few years. it's so odd.

Vonhelmet · 14 Jun 2007 at 21:38

I can do lots of mental arithmetic without much though, including multiplying two or three digit numbers... I don't know how.

One guy calls me Rain Man because I always divide restaurant bills in my head quicker than anyone can do it on a calculator.

Not that any of this bragging helps you in your numerical quest!

Stormrider · 14 Jun 2007 at 21:47

vonhelmet said:
I can do lots of mental arithmetic without much though, including multiplying two or three digit numbers... I don't know how.

One guy calls me Rain Man because I always divide restaurant bills in my head quicker than anyone can do it on a calculator.

Not that any of this bragging helps you in your numerical quest!

Do you actually do any calculations in your head or does the number just pop up?

[TR]SweetSpotOz · 14 Jun 2007 at 21:50

Firstly, you should learn everything up to 12x12 as it will probably stick with you quite easily.

Then Angus/Jokester's method is quite easy.

Stormrider · 14 Jun 2007 at 21:52

markyp23 said:
Firstly, you should learn everything up to 12x12 as it will probably stick with you quite easily.

Then Angus/Jokester's method is quite easy.

I still remember having the times tables drilled into me at primary school.
Do they even still teach kids that anymore?

Vonhelmet · 14 Jun 2007 at 21:52

Stormrider said:
Do you actually do any calculations in your head or does the number just pop up?

For the simpler ones, I don't do anything consciously.

I'm very good at identifying whether a number is prime or not just by looking at it. That's a pretty weird one. I'm not perfect at it, but often enough that it freaks me out.

Glaucus · 14 Jun 2007 at 21:55

Stormrider said:
I still remember having the times tables drilled into me at primary school.
Do they even still teach kids that anymore?

I only got taught up to the 10 times table, then the grid method.

Stormrider · 14 Jun 2007 at 22:03

vonhelmet said:
For the simpler ones, I don't do anything consciously.

I'm very good at identifying whether a number is prime or not just by looking at it. That's a pretty weird one. I'm not perfect at it, but often enough that it freaks me out.

I'm not sure to be jealous of you or just look at you in a strange way

AcidHell2 said:
I only got taught up to the 10 times table, then the grid method.

up to 12 times here, but thats such an age ago, plus I hardly use the knowledge anymore, so I doubt I'm that sharp anymore.

anyway, thats what calculators are for

manoz · 14 Jun 2007 at 22:05

I do it i chunks like Jokestar, have no idea what the grid method is. People have on occasion told me what a nerd/geek I am for doing the math rather quick

Glaucus · 14 Jun 2007 at 22:11

manoz said:
have no idea what the grid method is. P

not very easy to do in the head.

manoz · 14 Jun 2007 at 22:23

AcidHell2 said:
not very easy to do in the head.

Hmm, yeah not so inconvenient in the head. I see where the numbers in the square bits come from and you would just add them up but I don't see what the diagonal lines are for?

Glaucus · 14 Jun 2007 at 22:25

manoz said:
Hmm, yeah not so inconvenient in the head. I see where the numbers in the square bits come from and you would just add them up but I don't see what the diagonal lines are for?

you have to add up in a diagonal. excellent for working out any large number easily, but not nice for mental arithmetic.

[TR]SweetSpotOz · 14 Jun 2007 at 22:26

manoz said:
Hmm, yeah not so inconvenient in the head. I see where the numbers in the square bits come from and you would just add them up but I don't see what the diagonal lines are for?

Diagonals are because you add each diagonal to get the product.