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On my Mac's calculator entering in
100-50/2 = 25
On iOS7 on an iPhone 4S entering in
100-50/2 = 75
Hitting clear a bunch of times, even AC and trying
100-49/2 = 75.5
On the Mac's calculator it's
100-49/2 = 25.5
Is this normal or am I just doing something wrong?
On the Mac you don't have to hit Equal after 100-50 but it seems you do on the iPhone which seems bizarre.
Any ideas?
The correct mathematical order of operations for the equation that you posted 100-50/2 is to first divide 50/2, answer 25, then subtract 25 from 100, answer 75. Order of operations is not from left to right as in 100-50, answer 50, then divided by 2, answer 25. Order of operations is parenthesis, exponent, multiplication, division, addition, then subtraction.
The correct mathematical order of operations for the equation that you posted 100-50/2 is to first divide 50/2, answer 25, then subtract 25 from 100, answer 75. Order of operations is not from left to right as in 100-50, answer 50, then divided by 2, answer 25. Order of operations is parenthesis, exponent, multiplication, division, addition, then subtraction.
The iPhone calculator follows standard mathematical precedence rules, which state that in a series of calculations multiplication and division are evaluated before addition or subtraction. The built in Mac calculator uses arithmetic precedence; it just performs operations in the order entered.
The calculators on my Windows computer and iPhone 5S behave exactly the same. I believe this has to do with the fact that the iPhone calculator does not store the calculation and perform it all at once. As you type it in, it will do the 100-50, then divide by 2. It more than likely has to do with the design of the calculator. Not all calculators will store the entire problem and execute it all at once. Granted, this is my opinion, but I believe that as you enter the 100-50, then hit the divide sign, it calculates that first section, then you enter the 2 and equal, that is why you get the answer you get.
There is only one correct answer to each of those equations, and only the second and third are. My Macs, iPhones and iPads all calculate correct answers.
If you want to evaluate 100-49/2 it is not correct to hit equal after 100-49, unless you want 51 as an interim result.
It's acting more like it's adding them. The result is 75 after diving by two. What's 75 after diving by two, 150.
So, the iPhone calculator is acting like it's adding 100 and 50 THEN dividing by 2 to get 75.
100-50 / (here it seems to add them rather than subtract to "store" 150) then divides by 2 to output 75.
It's so weird.
I don't get it.
On my iPhone if I type in (after hitting clear a few times)
100 - 49 / 2 then hit the equal sign I get 75.5
If I enter in
100 - 49 Equal Key then Divide Key then 2 then Equal Key I get 25.5.
On my mac the answer is 25.5 using both methods.
Woudn't that make the answer -75 then?
100 - 50 /2 = -75
50/2 - 100?
Maybe I've just been out of school too long (decades) but this seems like wrong behaviour to me.
On my iPhone if I type in (after hitting clear a few times)
100 - 49 / 2 then hit the equal sign I get 75.5
If I enter in
100 - 49 Equal Key then Divide Key then 2 then Equal Key I get 25.5.
Those are both correct. What Mac OS X version are you using?
100 - 50 /2 is evaluated as:
Division first: 50/2 = 25
Subtraction next: 100 - 25 = 75
Any scientific calculator will evaluate that expression as 100 - (50/2). The Mac is evaluating it as (100-50) / 2
Neither is "right" or "wrong". You just have to know whether the calculator is following mathematical evaluation rules or left-to-right evaluation rules.
There should be a toggle for left-to-right and order of operations 🙂
This has messed up a few people more than a few times as I searched around for it it seems.
Thanks for all the replies. I'll have to get into the habit of hitting Equal on my phone while I'm not in the habit on the Mac.
The calculator in Mavericks on my MBP uses left to right precedence. Which is wrong. And which is why I never use it.
Mavericks' Calculator.app is observing correct algebraic hierarchy here:
| key | display |
|---|---|
| clear | 0 |
| 100 | 100 |
| minus | 100 |
| 50 | 50 |
| divide | 50 |
| 2 | 2 |
| equal | 75 |
Yours isn't doing that?
John Galt wrote:
Mavericks' Calculator.app is observing correct algebraic hierarchy here:
key display clear 0 100 100 minus 100 50 50 divide 50 2 2
equal 75
Yours isn't doing that?
Using the calculator on the widget screen it is displaying 25. Using calculator.app it does it correctly.
iPhone Calculator Wrong Order of Operations?
