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

my_gorgeous_ellie-belle

wildthing01 wrote: »

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....

This is so true. Understanding the figures is so much more important that some of the memorsing techniques. My OH learnt by memorising, which meant after a year or so after school, not using the memory technique regularly he'd forgotten everything completely.

I on the other hand had a fantastic teacher who would welcome questions of why does this equal such and such, he'd go on to explain and make sure we could then play with any amount of numbers and get the right answer. It was all about understanding the numbers and techniques, not just memorising!

That said my OH had to do a maths and stats test to get his job, he really struggled and failed the first time around. He had to wait a year to apply again but in this time we went to buy very basic childrens maths excercise books for him to 'start again from scratch'. I am talking books as basic as 7yrs. Second time around he got the job and actually got 95% on the test and came out with the highest mark. For the first time ever he'd been the best at something academic.

But three years on without any practise apart from the occasional shopping trip, he now knows exactly how decimals, percentages, division, fractions ect all work and how many are in fact the same thing in a different format. Its nothing amazing, he's no math genius or anything but if it weren't for going back to the basics he'd have been lost and would never have got his job he has now.

His brother then went for a job with the same company and also failed the math test. He advised him to go and buy the kids maths books but he was too proud so is still stuck in his dead end job. It's a shame really as there is nothing wrong with learning from a kids book if it means you'll understand the skill in the end.

my_gorgeous_ellie-belle

redux wrote: »

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.

You can break it down quite easily though with estimations:

2x 400g = 800g (for offer price of £5)
to get the same with the other - value wise it be:

you need to work out how to change the 600g to the same as he new 800g offer so that an extra 200g (ie 1/3 of the 600g), Divide the £4.29 roughly by 3 = £1.43 (i think) so add that to the original £4.29 = £5.72

So while the offer is on the offer is better value, otherwise, the 600g pack is better value to weight ratio normally.

But to be honset i usually go by what i need to use only. I rarely buy extra even if it is on offer unless i know we'll certainly use it

Sometimes it gets much harder. I rarely bother work it out either then then

redux

thank you, but I wasn't actually asking for help

cattarn

I voted A, but then I do have a maths degree and teach maths to 9-13 year olds - so I use mathematical thinking on a daily basis for work as well as shopping! I do agree that shop maths is rarely as simple as 30% off though as then you have to compare value across different pack sizes / 3 for 2 deals. Oh well, at least I can relate the maths in school to what happens in the real world so the kids see there is a reason to be in the lesson!

Eco_Miser

A lot of people are saying to get 30%, divide by 10 then multiply by 3. Often multiply by 3 then divide by 10 is easier - as in the example 16.99 round to 17. 3 17s is 51 (treble 17 in darts) 10% is 5.1.

And as said dividing by 4 for 25% or 3 for 33% is easier - at least for those of us who can do simple division.

manic_cow

KeithSheppard wrote: »

The sample question isn't maths, it's arithmetic. There's a real difference. I have a maths degree. I have used (eg.) calculus many time in adult life but mathematicians are notoriously bad at arithmetic.

I can manipulate the formulae and love algebra, but I cannot add up to save my life. That's what computers are for.

I agree with this, I loved maths at school (yeah I know I'm sad ) and I can do algebra til the cows come home but I'm not so hot on mental arithmetic. I blame my memory in some cases, by the time I've worked out one part I've forgotten the other part I was meant to add it to! I'm fine if I've got a pen and paper though.

Times tables are important for kids I think, if you've got those memorised it gives you a good base to work from. I'm much better at working out anything involving 7s as one of my teachers forced me into learning that times table for weeks on end. It seemed boring as hell at the time but I understand why now.

pepe2008

Just checked the results and they add up to 101%

brightonman123

i guessed poll discount was £5, just 10p out!

butterfly72

I try and do percentages in my head by rounding up or down and breaking things down into bits. I normally get there.. but it does mean I spend a fair while in the supermarket sometimes!!

I recently found these free OU maths courses. Some of them seem to start at the basics:

http://openlearn.open.ac.uk/course/category.php?id=8

Tarry

I can do some with a calculator, not particularly strong with percentages though.