Casio calculators incorrect calculations

clintondaly

I couldnt find somwhere more appropriate to post this but if there is please move it.

i had been working out some figures for a work related item and couldnt find my normal calculator so i borrowed a colleagues and started using it,i was working out the addition of a percentage onto some figures,after a while i discovered that the numbers didnt make sense to me.

i then went and borrowed another calculator and done the same calculations i got a different set of answers.

to prove to myself that the Casio answers were wrong i done some simple maths 100+10% the Casio gives me an answer of 111.11111,i tried on several other brands and all have given me the answer i expect of 110.

I then went around and tested the theory on other Casio calculators within our company and got the same result 100+10% comes out at 111.

I suggest you try it for yourself.


My question is
is this something unique to Casio calculators,is the problem responsible for global downturn.

Rgds

Confused

ThisRegard

Very interesting, just tried it on my calculator on my Galaxy phone and get the answer as 100.1.
And if you try it in google you get 100.1 also. http://www.google.ie/search?hl=en&q=100%2B10%25&meta=

Both are looking at 10% as literally being 10 percent of 1 as opposed to being 10% of 100 or whatever.

ConfusedLepton

100+10% doesn't make mathematical sense. You need to do 100*1.1 and there is no way you have a calculator that doesn't work out 100*1.1 correctly. I'd hazard a guess that any calculator that returned 110 was just adding 10 rather than working out 10% of 100 and adding it on. Try doing 200+10% and do you get 210?

partyatmygaff

200 + 10% gets me 200.1 on my Casio FX991ES. 100 + 10% gets me 100.1

Presumably the % sign takes a certain percentage of 1. It isn't very mathematically robust anyway, the proper way of modulating a value by a percentage is to multiply it by a decimal representation of the percentage.

EDIT: If you're adamant about using the % operator however, you can just multiply instead of adding. For instance to find 200 "+ 10%" just type in 200 x 110%.

ThisRegard

ConfusedLepton wrote: »

100+10% doesn't make mathematical sense. You need to do 100*1.1 and there is no way you have a calculator that doesn't work out 100*1.1 correctly. I'd hazard a guess that any calculator that returned 110 was just adding 10 rather than working out 10% of 100 and adding it on. Try doing 200+10% and do you get 210?

Nah, it's a valid computation. 200+10% by your reckoning should be 210, but you'll get 220, apart from the 'dodgy' casio calculators

28064212

It's an ambiguous statement. 100 + 10% of what? There is no such figure as 10% on its own. The correct response from all the calculators would be to throw an error

ThisRegard

No, it assumes you want 10% of the figure you entered. I've used calculators for years this way. It's what the % function is designed for, for example if you want to get 25% of 120 you enter 120*25%, you don't explicitly say what the 25% refers to, it's implied. Same way as using the add function.

200*110% does the same thing.

28064212

ThisRegard wrote: »

Not if it's programmed to assume you want 10% of the figure you entered. I've used calculators for years this way.

Which is fine if there's some sort of consensus, but as this thread clearly shows, there's not. What would this mean: 100 + (÷10) ? The calculator could decide it probably means 100 + (100 ÷ 10), but it's actually just an invalid statement

clintondaly

Canon LS-83TC using 100+10% gives 110
Aurora SP800 100+10 gives 110
ibico 128S 100+10% gives 110
Casio DS-20 100+10% gives 111.1111111
Casio D-20TER 100+10% gives 111.11111
Casio M58TV 100+10% gives 111.1111111
Casio MS8S 100+10% gives 111.1111111



"Nah, it's a valid computation. 200+10% by your reckoning should be 210, but you'll get 220, apart from the 'dodgy' casio calculators"
200 + 10% on Casio gives 222.2222
on all other brands it gives 220

If the responses suggest that my calculation method is not correct in mathematical terms why then do i get different answers according to the brand of Calculator.

ThisRegard

28064212 wrote: »

Which is fine if there's some sort of consensus, but as this thread clearly shows, there's not. What would this mean: 100 + (÷10) ? The calculator could decide it probably means 100 + (100 ÷ 10), but it's actually just an invalid statement

It's not invalid, just because there's no consensus in this thread doesn't mean anything is wrong. Give me an example of how you feel the % operand should be used on a calculator ?

Is my example of 120*25% to get 25% of 120 valid ? And if so, why is it any different than using it to add ?

Katzi

When I worked in marketing and sales we ONLY used Casio calculators because they will work out MARGIN vs MARK-UP.

If you want to get 20% margin on a product costing say €100, with a Casio calculator you enter ' 100+20% ' and get 125. If you sell at €125 you are getting a 20% MARGIN.

If you want to know what 20% MARK-Up is then you enter '100 x 1.2 ' and get €120.

Huge difference between MARGIN and MARK-UP and Casio made this calculation easy-peasy when in meetings with buyers.

Cerco

Special Irish austerity version by Casio?;)

Different calculators use differnet methods. Some will accept the nonsense entry og x +10% as meaning x + 10% of x others will not. I can see how the feature simplifies markup calculations but all calculators will compute correctly if the entry is fully correct.

28064212

Cerco wrote: »

all calculators will compute correctly if the entry is fully correct.

Almost all: http://en.wikipedia.org/wiki/Pentium_FDIV_bug

byte

clintondaly wrote: »

I couldnt find somwhere more appropriate to post this but if there is please move it.

i had been working out some figures for a work related item and couldnt find my normal calculator so i borrowed a colleagues and started using it,i was working out the addition of a percentage onto some figures,after a while i discovered that the numbers didnt make sense to me.

i then went and borrowed another calculator and done the same calculations i got a different set of answers.

to prove to myself that the Casio answers were wrong i done some simple maths 100+10% the Casio gives me an answer of 111.11111,i tried on several other brands and all have given me the answer i expect of 110.

I then went around and tested the theory on other Casio calculators within our company and got the same result 100+10% comes out at 111.

I suggest you try it for yourself.


My question is
is this something unique to Casio calculators,is the problem responsible for global downturn.

Rgds

Confused

Heh, funny I should stumble across this thread, as it's something that also has been noticed at work when we got a few Casio hand calculators for on-the-go price calculations, always using the same process you've used with other calculators with no issue.

So back to using the no-brands and a few handy Sharp ones.

mathepac

clintondaly wrote: »

Canon LS-83TC using 100+10% gives 110
Aurora SP800 100+10 gives 110
ibico 128S 100+10% gives 110
Casio DS-20 100+10% gives 111.1111111
Casio D-20TER 100+10% gives 111.11111
Casio M58TV 100+10% gives 111.1111111
Casio MS8S 100+10% gives 111.1111111 ...

As expected on my ancient Sharp EL-531LH
100 + 10% = 110
200 + 10% = 220

On my even older free DENNY's Sausages Euro calculator
100 + 10% = 110
200 + 10% = 220

clintondaly

clintondaly wrote: »

I couldnt find somwhere more appropriate to post this but if there is please move it.

i had been working out some figures for a work related item and couldnt find my normal calculator so i borrowed a colleagues and started using it,i was working out the addition of a percentage onto some figures,after a while i discovered that the numbers didnt make sense to me.

i then went and borrowed another calculator and done the same calculations i got a different set of answers.

to prove to myself that the Casio answers were wrong i done some simple maths 100+10% the Casio gives me an answer of 111.11111,i tried on several other brands and all have given me the answer i expect of 110.

I then went around and tested the theory on other Casio calculators within our company and got the same result 100+10% comes out at 111.

I suggest you try it for yourself.


My question is
is this something unique to Casio calculators,is the problem responsible for global downturn.

Rgds

Confused

I can see why some calculators are giving 111.1111 for % and some 110 for 100 % 10. The calculators are not making a mistake.

Some are applying percentage markup and some are applying percentage margin.

So the calculators are not incorrect, they are doing different things.

10% mark-up on 100 is 100 * 1.1 = 110

10% margin on 100 is (100)/(1-.1) = 111.111111

With margin, in this case, 10% of the new price = 11.11111... , deduct that 10% and you get the original price of 100.

cicciopanza

from Casio support website:

Why do I get 111.1111... when I calculate 100+10%?
This is a markup on price procedure. The formula is as follows:
Markup%=(Markup Price-Cost)/(Markup Price)

Why do I get the wrong answer when doing a percent calculation?
Make sure that you are following the correct procedure.
Adding 10%: 200 [×] 10 [%] [+]
Subtract 10%: 200 [×] 10 [%] [-]
...

I think a 100+10%=110 is more usefull for users, all other brands do it
They say "why do I get a wrong answer...", sounds like they know it's wrong!

coylemj

I wouldn't even admit to owning a calculator with a % button!

cicciopanza

Sincerely, I have never seen a calculator without it.
Working with rates all day long I admit I am lost without that button. Shame on me

coylemj

cicciopanza wrote: »

Sincerely, I have never seen a calculator without it.
Working with rates all day long I admit I am lost without that button. Shame on me

As long as the function is consistent on the different machines you use over the years and you use it frequently on your work, good luck to you.

Katzi

When I worked in sales/marketing (a zillion years ago), Casio calculators were a Godsent because they enabled you to calculate profit margin on an item. If you wanted a 10% MARGIN on a product you could do this easily by entering +10%. This gave you €111.11 which represents a MARGIN of 10%. If you wanted a mark-up of 10% then you entered x 10% which gave you €110. Margin and mark-up are very different things and have huge implications to the profitability of a item.

All the sales managers in the company had Casio calculators for this reason. To calculate profit margin in a meeting on a normal calculator took a few steps, with Casio it was a piece of cake to work out what the price would need to be to generate a specific margin.

Not sure if Casio designed this feature for this reason. Sadly my old Casio died and my new one does not do this.