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

TigerTiger_2

KeithSheppard

Agree with your postings above but it is frustrating that they forget the basics that many of us will use most days in our adult lives.

I'm making my daughter learn her times tables all over again which has gone down like a lead balloon!

malc_b

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

Most likely is that the special offer you picked wasn't on special because the sign above the items was actually for something different. The number of times I've seen supermarkets make this "mistake", yeah right, just a "mistake".

And on a funny note, we once took back a chair, £19.99 for a refund as we decided we didn't want it. I'll give you the penny so you can give me a £20 note. Oh no, I couldn't do that it would throw the till out. Sigh!

OrkneyStar

£16.99 - 30%
I would do the following:
10 % = £1.699, so £1.70
30% = 3 x £1.70, so £5.10 off
so final price (100%-30%)= £16.99-£5.10= £11.89

eightwayliz

Hantopcat wrote: »

A - definitely

Why do you have to round up? What's wrong with 3 x £1.69?

Because it's 3 x £1.699 so closer to £1.70 than £1.69. If you actually meant why £1.70 not £1.699 then it's just easier maths for the sake of being less than a penny out at the end. Especially when you don't know whether the shop will charge £11.893 as £11.89 or £11.90

brokeinwales

I admit to being one of the dumb***es who voted D!

Anything more complex than basic adding up completely stumps me (even with a calculator). I have tried to improve my maths skills many, many times, but I'm afraid my brain just switches off when people start talking numbers - it's like a foreign language as far as I'm concerned. (Really bugs me when clever people do that thing "You just add X to Y and multiply by the square of Z and add 3 - it's really simple!" yeh right...)

Why do you have to round up? What's wrong with 3 x £1.69?

You can do that in your head??

I'm actually amazed how many people selected A and B. MSE is full of serious brainboxes!

OrkneyStar

davetrousers wrote: »

If you start with 100 then add 10% and then deduct 10% the answer is not 100.

Some people don't seem to understand this. It's a bit like people deducting 15% (or 17.5%) from a total price to work out the pre-VAT price.

100 plus 10% of 100 = 100+10 = 110
110 minus 10% of 110 = 110-11 = 99

To work out pre-VAT price:
Lets say price plus VAT = £10.99, this means 100% of the price pre-VAT, plus another 15 % = £10.99
So 115%= £10.99
1% = £10.99/115
100% pre VAT price = 100 x (£10.99/115) = £9.56
(work it back £9.46 plus 15% of £9.56 = £9.46 plus £1.43 = £10.99)

pepe2008

Get rid of the complicated bits ( ie the 99p ) by rounding up, it makes everything easier. When I worked for a Bank I could beat anyone who was using a calculator to add up a list of numbers, I put it down to playing darts in the pub with my Dad from the age of 12!

I made sure that my kids had the % calculating methods sorted out before they went into the big bad world...........seeing as the School didnt seem to bother.

wildthing01

there are lots of people going about calculating 33% and 25% discounts in very long-winded ways. for 33% just divide total by 3, for 25%, divide by 4. for anything ending in 0, divide by 10 then times by the number in the tens column (e.g. for 40%, divide by 10, times by 4).

i can't do anything more complex than that (e.g. trying to work out VAT at 17.5%). i got an A in my gcse maths, but i was allowed a calculator for that!!!

wildthing01

OrkneyStar wrote: »

100 plus 10% of 100 = 100+10 = 110
110 minus 10% of 110 = 110-11 = 99

To work out pre-VAT price:
Lets say price plus VAT = £10.99, this means 100% of the price pre-VAT, plus another 15 % = £10.99
So 115%= £10.99
1% = £10.99/115
100% pre VAT price = 100 x (£10.99/115) = £9.56
(work it back £9.46 plus 15% of £9.56 = £9.46 plus £1.43 = £10.99)

what?????????????

wildthing01

KeithSheppard wrote: »

Unless, of course, the battery runs out at the wrong moment.

I help out with numeracy in a local junior school for an hour each week and I whince every time I'm reminded of how they teach numeracy in school these days. Kids are very good at learning things by rote. If you tell a child the traditional method for doing, say, long division, most will be able to learn how to do it without necessarily understanding _why_ it works. For most people, the "why" will be irrelevant to their adult life.

The accent in schools these days is too much on understanding why numbers work the way they do. They teach kids various "strategies" for tackling numeric problems and expect each child to use the strategies they are most comfortable with. Many kids find this totally confusing and would be far better off if you told them "this is the way to do it".

I do agree with your youngest, though, that arithmetic isn't a significant part of maths once you get past a certain level (see my other posting).

OK, my rant over.

if you work in a school, you should be aware that different children have different learning styles and each should be able to learn in the way that suits them best. the reason i got an A in my maths GCSE was that i made the effort to understnad how the numbers worked - so even if i forgot the formula, i could work it out. my friends who simply rote learnt did not do so well......... true i'm not great at mental arithmetic, but i can problem solve....