Not Stupid, Just Uneducated.

[sandyRoe]

I was buying an item in the grocers this morning which was marked reduced by 25%. The original price was £2.80.

The lady went to the calculator on her phone to do the maths.

I told her the answer and when she'd checked she said you're right.

Do the schools not teach mental arithmetic any more?

[Ellipsis]

At work, somebody once asked me "What's thirteen add five?" ...

[youngmafbog]

Did you tell them it was 19?

[Peter Pedant]

I did Maff A level and still do these calcs in my head.....

[sandyRoe]

The new price was £2.10 in case anyone is interested.  ;-)

[Old_Geezer]

But it can't be. If I add 25% onto £2.10 then that comes to £2.62½ not £2.80 !!! 😲

[-SharonA-]

25% is 70p

So £2.10 plus 70p equals £2.80

 

[youngmafbog]

^^ Whoosh!

[ToraToraTora]

13:26 that's why you don't do that to reduce 2.8 by 25% you multuply by 0.75 = 2.1. To get back divide 2.1 by 0.75 = 2.8

 

[youngmafbog]

Its TIC TTT!

[Khandro]

I'm hopeless at mental arithmetic. My brain seems only hard-wired for visual things. If I had to do that sum, I would think a quarter of 2 pounds is 50p. & a quarter of 80p is 20p which equals 70p. Take that from £2.80. makes £2.10.

Quite a bit of effort for me, so I'd reach for the pocket calculator any time.

How would you do it? 

[Old_Geezer]

🤣

[Old_Geezer]

Pretty much as you did Khan.

[ToraToraTora]

khandro just look at the 2.8 as 28 . 4 sevens are 28 you want to leave 3 of them so 21 now put the point back 2.1 .. £2.10. tada!

[Ellipsis]

> Did you tell them it was 19?

I asked them (in the nicest way possible) how they could possibly do their job, which did involve numbers!

The answer was that they'd just had a brain freeze ... 

[Khandro]

There is a story (probably apocryphal) that when Einstein was a child in school, the teacher wanted to leave the classroom & wished to give them something to do while she was out, so she said, "Add up all the numbers from 1 to 100. 

Before she reached the door Einstein put up his hand & gave the answer. 

What he had seen, & something I can relate to, is that if you visualise all the numbers as laid out in a row & take the first and the last they add up to 101, then take the second and the penultimate & they also add up to 101 keep going and he saw you could pair up the numbers so that each pair adds up to 101, as follows:

1 + 100 = 101

2 + 99 = 101

3 + 98 = 101

…

48 + 53 = 101

49 + 52 = 101

50 + 51 = 101

Thinking about it this way, it becomes fairly obvious that the answer would be 50 x 101, which becomes quite doable in many people’s heads as 5,050. - Even mine. 

 

😃

[Radagast]

I've heard that story attributed to Gauss.

https://www.nctm.org/Publications/TCM-blog/Blog/The-Story-of-Gauss/

[Atheist]

Yes, Gauss, not Einstein.

[ToraToraTora]

very simple formula, numbers from 1 to n = (n+1)x(n/2).

so 1 to 100 = 101*50

fun fact all the numbers on a roulette wheel add up to.... 37x18=666!

[barry1010]

OG has pointed out the mistake many people make when trying to work out how much VAT they paid on their purchase.  Easier now at 20% than it was at 17.5%

 

[jourdain2]

Sandy - I think Ican better all of these.  The new chap next door (29, single, - doesn't speak, works from home on computers) put a note through our door asking  for our share of payment for the electricity for the running of the klargester for the septic tank.  We knew a few quid were in order per month, but he'd queried the exact amount and OH had asked him to send us a bill.

We went round and asked... £3.00 per month he reckoned. We're not arguing, we thought about the same.  Anyway, he said thatwe hadn't paid for 8 months (we didn't know how much he wanted) so I said, "OK, 8 threes is 24 - we owe you 20 quid."  He looked at me, baffled.  Turns out he's an accountant!!

I told him that it was easy to see that he hadn't been educated in the 1950s.  :)