Bad Math at Wolfram Alpha (Or Not?)

https://www.wolframalpha.com/input?i=1%25+%2B+3%25

by mfcc64 • 4 years ago

9 10 4 years ago

civilized2• 4 years ago

In the real world, the right answer is to acknowledge ambiguity and make sure you understand the context and what the person is asking. But without that context, if you must give an answer, this is the best one. Adding 3% to anything means multiplying it by a factor of 1.03. For uniformity, this must include percentages themselves.

Differences between percentages are called percentage points, so if you want to add 1% and 3% and get 4%, you should call the second term "3 pp".

This will seem outrageous to many programmers, who will understandably want two numeric-looking things of the same type to add in the ordinary way. But percentages don't work that way. They're a shorthand for a non-additive operation so they have different rules.

injb2• 4 years ago

I agree about clearing up ambiguity. But I'm not convinced that there's a best way to answer it without context.

For instance, enter "1%" into Wolfram and it'll tell you it's 1/100. Do the same for 3% and it'll tell you it's 3/100. Now ask it to add those 2 fractions, and it'll obviously give you 4/100 - which it reports can be expressed as 4%.

These are supposed to be alternate representations of the same thing, so arguably the answer shouldn't be different.

civilized2• 4 years ago

I agree, choosing a single answer at all is a bit weird here.

beardyw• 4 years ago

Though to be fair in normal usage 100 + 3% would be 103. I feel there is an implicit "of it" after 3% which you wouldn't expect with 3/100. I think it's accountant maths.

nh23423fefe2• 4 years ago

but `+` is polymorphic in the inputs as is `print`

just because `print` does one thing doesn't really mean `+` is constrained in the same way

gowld• 4 years ago

This will seem outrageous to many programmers, who will understandably want two numeric-looking things of the same type to add in the ordinary way

What is 1 o'clock + 1 o'clock?

ncmncm• 4 years ago

This is the "wrong result can be justified on a technicality" argument. But a wrong result is just a wrong result. How you got there is immaterial except insofar as it offers you clues on how to fix it.

Mathematica is well equipped to recognize the circumstances that produced the wrong result, and produce the right result instead.

That involves work, but Mathematica has kept a stranglehold on the product specifically in order to extract the revenue that could be used to pay for such work.

nh23423fefe2• 4 years ago

asserting wrongness isn't persuasive in the face of ambiguity

Bad Math at Wolfram Alpha (Or Not?)

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