'Can you do percentages in your head?' poll discussion

SailorSam

They never had tiny calculators when i was first leaning to count so it's second nature to work things out in my head.
I'm ok up to 10, after that i need to take my shoes and socks off.
I hope i never need to count any higher than 20 though.

OrkneyStar

John-the-Handyman wrote: »

I don't necessarily agree with some of the ways mentioned. I find it's much easier to do this.....

To calculate the reduced amount. If the deduction is 30% (i.e.30 per hundred) then the remaining sum will be 70% of the price.(100-30) (or .7 if you prefer. i.e seven tenths. 70/100 is the same as 7/10 or .7/1) So you just have to multiply the amount by 7 then move the decimal point back one place. £16.99 times 7 = 118.93 Therefore you will pay £11.89
Simple.

To work out the VAT inclusive price on anything just multiply the initial figure by 1.175 To work out the VAT free price it follows therefore that you just have to divide the VAT inclusive price by 1.175 Saves all the adding or subtracting bits or sums. Does it all in one go!

Life is as easy or as difficult as you make it.... I think.. i think I think... I'm sure I think I think. Well-perhaps. Oh I dunno......!:j

Yes that works too, however I explained it the way I did in the hope it might make more sense to someone trying to understand the calculation. If you understand why you do something you are more likely to remember how to do that something iyswim!

gilligansyle

shellsuit wrote: »

I voted B.

I always do it with 10%, so in the example above, I'd do 10% off then times it by 3.

Where there is a 5%, I still working it out using 10%, then halve it.

If it's something else, for example, 33%, then I'd find it a little difficult to do it in my head so I'd just do 30% and know I'd be saving a little more extra too.

Me too, except that of course 33% is easy, its just divide by 3.

mazza111 wrote: »

Percentages no problem, estimating my shopping trolley on the way round never works, i'm sure the supermarket fairies put stuff in there without me adding it

I always round up as I'm going round but without the offers, so if something is BOGOF I still count both, then I will always have enough when I get to the till and know I will be in budget.

scotsbob wrote: »

I can do most percentages in my head.

That is because I went to school in the 1950s and at the age of 10 the teacher gave us a good belting if we didn't know them all mentally.

If I went to school today I would probably need to progress to maths at university level to know what a percentage was.

I went to school in the 60's and we spent the first half hour every day doing spelling and mental maths, so its a bit second nature to me. Colleagues could never understand how I could work out VAT in my head faster than they could on a calculator.

Taffybiker

glossyhair wrote: »

I always shop with a calculator. Sure I must look like a right numpty but needs must when every penny counts!!

You could use the calculator on your mobile phone - people will think you're texting - lol

magpiecottage

There are, in fact 10 types of people when it comes to maths.

Those who understand binary and those who don't.

Princess_Jane

D for me as I have dyscalculia or maths dyslexia.

You might as well be shouting Russian down a garden hose at me for all the sense percentages make and once I run out of fingers and toes I'm knackered.

wildthing01

cheepnis wrote: »

@ wildthing01


if you can divide by 10 and divide by 2 then for VaT @ 17.5% you'll only need a biro :santa2:

• Bill = £100-00
• start with 10% = £ 10-00
• divide that by 2 = £ 5-00 (5%)
• divide that by 2 = £ 2-50 (2.5%)
• add them up = £117-50

that's really clever!! never thought of it like that!

bylromarha

Long live the grid method and partitioning.

Most kids actually understand what they are doing with numbers and know if their answer is realisitic or not - a calculator can't help if you accidentally press the wrong button and get a wrong answer, a lack of understanding of the question doesn't highlight that you've boobed on the calc.

I was able to do long division with algebra long before i could do it with numbers. mathematical processes are pointless if you don't understand what's happening with the numbers.

my_gorgeous_ellie-belle

scotsbob wrote: »

I can do most percentages in my head.

That is because I went to school in the 1950s and at the age of 10 the teacher gave us a good belting if we didn't know them all mentally.

If I went to school today I would probably need to progress to maths at university level to know what a percentage was.

Lol, erm not quite, i went to school just 9 years ago. Percentages are a piece of cake by the age of about 12. I got an A, and A in my additional GCSE statistics, many just couldn't be bothered hence failed. I fell off the good track when it came to college though so dropped out of A level maths a year in Needed money as i was living alone paying rent, bills and couldn't afford to eat some nights through so little cash. So the work bug caught me.

I don't agree with the use of calculators in primary schools though, that didn't happen when i was at school, not at least until you reached secondary level and had to use scientific calculators for pie and the many other 'more complicated' calculations, even then we was taught to do what we could in our heads/on paper. Sadly it does now, 7 yr olds are using them, the basic ones for basic maths

Easiest way in your head is to say 10% is Y (move the decimal place over one digit to the left for 10%), so: 30% = 3 x Y

I always amaze my OH as i do calculate the shopping in my head once we get to the till. Him and DD have to be quite as i am mentally adding it up as i put it on the belt. I estimate everything to the nearest 10p and add it all up (i am pretty savvy at knowing what roughly costs what though i must add - wouldn't work otherwise). It is never more than £1 or £2 off even if it's a big over £100 shop.

My OH though, if he pulls out a handful of change he'll stare at it for ages all bemused, hehe! I love it, really makes me laugh! But he's great at other stuff that i'm not so good at. :rotfl:

redux

Of course the arithmetic that might be needed in shops isn't as simple as the example of 30% off £16.99

For example yesterday I looked at some cheddar cheese. Cutting down gradually to considering one brand, one packet size is marked as 600 g and costs £4.29. Or there are 400 g packets for £3, but with a buy 2 for £5 offer. The latter says it works out to £7.50 per kg. But that doesn't mean with the combi offer, even though it's written on the same ticket.

Same goes for yoghurts. One brand has 2 offers. 3 for £1. Or 2 packets of 6 for £5. That one's probably a bit simpler to work out than the cheese.