Does anyone NOT know the 9 times table finger trick?

[DilemmaDelilah]

I was having lunch today with my DH and one of my grandchildren and we were idly trying to work out the weight of a McVities ginger cake. It doesn't have the weight on the packet, but it says that it has 9 portions each of 25.8g, so we were doing some mental arithmetic to work out the weight (for fun only... It wasn't performative grandparenting). Anyway - I was working it out the way that is easiest for me, which is to break the sum down into its component parts, i.e. 25x4, plus 25x4, plus 25, then 8 x 9 and add in the decimal point, then add them altogether which is, apparently, the autistic way (I am autistic) but seems ultra logical to me. This involved, obviously, working out 8x9. I did my usual finger trick to remember the answer and neither DH nor my grandson has ever heard of it!

It uses the fingers of both hands as a reminder. Bend down the first finger, that leaves 9 fingers, that means 1 x 9 is 9. Bend down the second finger, that leaves 1 finger and 8 fingers = 18, therefore 2 x 9 is 18. Bend down the third finger, that leaves 2 fingers and 7 fingers = 27, therefore 3 x 9 is 27 and so on....I thought this was something everyone knew, but apparently not! How about you lot? And does anyone else have any equally easy ways of remembering maths? My DH and grandson thought it was magic!

Jonny Ball!

I've never heard of this!

I have never heard of that finger trick and it sounds far too complex to be useful! and also your way of calculating the sum seems completely illogical to me (and I’m also autistic) - surely the most logical way is to work out what 10 portions would weigh and then subtract the weight of 1 portion to get the weight of 9 portions.

I think most people just memorise their 9x table at a relatively early age. So something like that would be useless.

I learnt my tables up to 12x decades ago rote and still haven't forgotten them even though I barely use them.

Sorry.

We were taught it at primary school, I still occasionally use it now!

Also, how does your trick work for 11x9 and 12x9?

I learnt this as a child and still use it today when I need to know 9 times something.

Never heard of it

I also learned tables by rote

So I would calculate that by 25×9 = 2 25

.8×9 = 7.2 - which I'd know from my eight times table or nine times table.

no waving fingers around!

It's a brilliant trick and I've taught it to many children over the years who have then passed it onto their grown ups who didn't know it. It's a very handy way to work them out if you never learnt by rote which many adults (myself included) didn't.

I do

Johnny Ball - Think of a number.

Take 90 and add 9 or 18

Also, if you aren't sure, the didgets add up to nine!

They do indeed and as the tens go up the ones go down in numerical order.

09
18
27
36

And so on. The 9 times table is actually one of the easiest to teach to children thanks to all the tricks.

I learned my times tables up to 12, by rote, 65 years ago, never forgotten them!

I use the finger trick. And I taught it to my DC

So far we seem to be fairly evenly split between those who scoff at it and those who find it useful! No need to wave fingers around... one can be discreet! I hadn't even thought about timesing by ten and then taking away - that seems more difficult to me. And - as somebody has already said - for 11x9 and 12x9, just add 9 or 18. I'm all for things that make other things easy - I'm not too bad at maths but I can't be bothered with fiddly stuff in my head - I'd rather use pen and paper for that. I spent many years pre-university working behind a bar and adding up large and complicated rounds in my head... so I'm not incapable!

Yes it’s a great trick!

Yep, I’ve taught it to my eldest recently!

Yes, of course.
and it’s definitely not too complicated to use. I’m one second you have put a digit down on a hand and seen what is left and have an answer.

Nope, learnt my tables, so can do the sum without resorting to digits. Which of course won't work if you've had any fingers amputated. I suppose toes could be used as a substitute, but the little one doesn't bend over, so you could only do 8x9. Plus you need pretty feet if you want to do 9 x calculations in the middle of Waitrose

For that sum my default approach is/:

25x 9 which I’d break into 10x9=90 , plus another then another 90 plus then half of that… so 225

then I’d do 8x9 - move the decimal point

anf add to 225

Yep! Always done it that way! I am always surprised people don’t know it. Pretty sure I learnt it from a times table video with Carol Vorderman 🤣

Surely it would have been easier to work out 10 portions and subtract one portion.

I've never seen anyone need their fingers for the 9 times tables.

Never needed to memorise 9x table because of this trick, (except the 9x11, 9x12). I still use it to check my maths.

(Maths grad) 😂