Many calculators not following math rules?

[Kaotik]

And it's a damn simple equation too:
48 / 2 ( 9 + 3 )

Basic math rules say that you first calculate things within parenthesis (if there's more than one, you start from possible parenthesis inside another parenthesis etc), multiplying and dividing are equal and done in order from left to right.
Also since there's parenthesis next to number without anything between them, they're multiplied.

So the above equation goes like this:

48 / 2 ( 9 + 3 ) =
48 / 2 ( 12 ) =
24 ( 12 ) =
24 * 12 =
288

However, some calculators count it like this:

48 / 2 ( 9 + 3 ) =
48 / 2 ( 12 ) =
48 / 24 =
2

Strangely enough, some people are quite convinced the latter way should be correct, and not the former.

Here's wolfram alphas take on it:
http://www.wolframalpha.com/input/?i=48/2(9+3)

And examples where calculators fail or do it right:

 

[3dcgi]

Strange that not all Casios are the same. I assume you meant multiplying and dividing are equal even though you wrote subtracting.

 

[Kaotik]

Strange that not all Casios are the same. I assume you meant multiplying and dividing are equal even though you wrote subtracting.

gah, i knew i made a mistake, was originally writing "multiplying and dividing are calculated from left to right, adding and substracting are counted after those again from left to right, but decided shorter is better and there's no adding/substracting other than within the parenthesis so doesn't really matter

I'll fix that

 

[Bludd]

I have a TI-83 and it gives 288 as a result. I also have an HP 30S and it gives 2.

http://www.google.com/search?q=48%2F2%289%2B3%29

 

[Davros]

remember the calculator in windows had errors and they offered an update

Steps to Reproduce Problem Using Previous Versions of Calculator
To perform this test, choose two numbers that include values to the right of the decimal point (for example, 12.52 and 12.51).
Double-click the Calculator icon in the Accessories group.
Enter the larger number first (for example, 12.52).
Press the MINUS SIGN (-).
Enter the smaller number (for example, 12.51).
Press the EQUAL SIGN (=).
Note that in this example you do not receive .01, the expected result. Instead, you receive one of the following:
0.00
0.0099999999
0.010000001
The updated Calculator accessory displays the correct result, which is .01.

 

[Bludd]

Anyone have PowerCalc from Windows XP Powertoys? The calculator in Win 7 doesn't really handle inputting this equation.

 

[CNCAddict]

TI-30XS calculates 288.

P.S. The TI-30XS is one of the best cheap calculators I've found. For all my uses works the same as a TI-89 with the up arrow going through the history of calculations.

http://education.ti.com/educationportal/sites/US/productDetail/us_ti30xs_mv.html

 

[3dcgi]

I wish someone made a good programmer's calculator with dedicated ABCDEF keys. RealCalc for Android isn't bad, but I'd like a dedicated calculator with a multi-line screen. My TI-85 has the features I need they're just buried in menus. My TI-85 has been quite the workhorse. I got it in 1993.

 

[WhiningKhan]

TI-85 calculates it correctly if you don't omit the multiply sign from the equation. Remember that you are actually using a programming language in this case - it is not completely the same as classic arithmetics.

Consider this:
A=12
48/2A

You get 2, which is intuitive. When you are omitting the multiply sign, the interpreter handles it like a macro expansion and calculates the value of denominator first.

 

[Kaotik]

TI-85 calculates it correctly if you don't omit the multiply sign from the equation. Remember that you are actually using a programming language in this case - it is not completely the same as classic arithmetics.

Consider this:
A=12
48/2A

You get 2, which is intuitive. When you are omitting the multiply sign, the interpreter handles it like a macro expansion and calculates the value of denominator first.

But it's not 2A, it's 2(A), which is completely different, and indicates there is multiply sign in between.

 

[Bludd]

HP 30S also does it correctly if you multiply explicitly

48/2*(9+3)

 

[WhiningKhan]

But it's not 2A, it's 2(A), which is completely different, and indicates there is multiply sign in between.

It's doing numeric evaluation, not classical algebra. I believe the parentheses trigger partial evaluation, and by leaving out multiply sign you are indicating tight coupling for evaluation order.

 

[NRP]

Moral of the story: Don't get lazy - enter your operator signs

 

[Mize]

HP RPN FTW. Too bad they don't make the 15C anymore. Best damn calculator ever. I've had mine since 1980 and it's still the best.

edit: 15c not 16c

 

[Grall]

My TI-85 has been quite the workhorse. I got it in 1993.

Me best mate bought a Casio calculator with a solar cell and rechargeable battery built-in for use in highschool. This was roughly 1990...and he still uses it.

The rechargeable battery's worn out (NiCD prolly, well before NiMH), but the solar cell still works just fine.

 

[Mize]

'93? '90?
Bah. Lightweights!

1980 bitches!

 

[Davros]

Anyone have PowerCalc from Windows XP Powertoys? The calculator in Win 7 doesn't really handle inputting this equation.

is this it ?
http://windows.microsoft.com/en-US/windows/downloads/windows-xp

The most i ever did with a calculator is type 5318008 and turn the calculator upside down

 

[Bludd]

is this it ?
http://windows.microsoft.com/en-US/windows/downloads/windows-xp

The most i ever did with a calculator is type 5318008 and turn the calculator upside down

Power Calculator
http://go.microsoft.com/fwlink/?LinkId=211474

Anyone with XP could try this and see how it does with the equation?

 

[Albuquerque]

Power calculator doesn't like the equation as-typed:

I went through several iterations, but it needs the multiply character directly stated, it will not imply it. I'm on board with the "2 as the right answer" theory, only because (as someone else mentioned) the 2(9 + 3) gives an implicit expectation of precedence.

But since this behavior isn't well defined, I'm not sure if it's actually the correct answer.

 

[nintenho]

I think most people who have taken calculus would get 2 as their answer. In math and science textbooks they often stretch out long arithmetic expressions for example:

n=PV/RT (T is often written as a sum)

99% of the time the ideal gas law is written that way which could be incorrect if entered into a calculator with T being a sum of two numbers. So for the equation in the OP, 2 is the wrong answer but a lot of people are just used to that form by now.