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I'm no longer able to multiply scalars by quantities in Mathematica 11.3. In previous versions the code

3*Quantity[1, "mm"]

evaluated to

3 mm

Now it returns

3(1 mm)

which throws errors in subsequent calculations.

Multiplying quantities by other quantities still works fine.

Assuming this change is not a bug, but intentional, how am I supposed to multiply quantities and scalars in 11.3?

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It works on my Mathematica 11.3 on Windows 10 as you expect, i.e. returns

3 mm

Try restarting the kernel.

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I saw the behavior like this just yesterday after recently installing Mathematica on that machine. The Duration function applied to an Audio returned a form, IIRC SomeContext`Quantity[SomeContext`UndefinedQuantity[3.141`, "s"]]; I do not remember what the context was. I did not pay much attention to that, as I got the result I wanted, albeit in a weird form; some time after, when I evaluated another expression involving a quantity, I saw a PrintTemporary-generated output cell with a message to the effect "Downloading from Wolfram server (xx%)" with the progress value xx ticking from 0 to 100, and quantities magically began working. I think you are hitting a bug.

Please try to figure out what would trigger the download of the missing package, and file a bug.

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This is not an answer, just a comment.

I am experiencing a similar issue but I have noticed it when dealing with time quantities. I have to quit Mathematica to restore the normal behavior. I don't know what triggers it but I have a small notebook on my second monitor with this dynamic expression which I'm hoping will help me figure this out:

Dynamic[If[(-Quantity[1, "Minutes"]) + Quantity[1, "Hours"] == Quantity[59, "Minutes"],
  SetOptions[EvaluationNotebook[], Background -> LightGreen]; "OK",
  SetOptions[EvaluationNotebook[], Background -> Red]; "NOK"], 
 UpdateInterval -> 2]
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  • $\begingroup$ Mine is also about time (see my non-answer). Did you see the download progress as I did, or any of there unevaluated form returned instead of time? Just wondering if we can narrow it down to the level of reproducibility suitable to open a bug case. I, for one, am unable to repro the issue. $\endgroup$ – kkm Jul 10 '18 at 16:34
  • $\begingroup$ During my regular workflow, I rarely see the downloading from wolfram messages. However I use the network functions a lot (HTTPRequest and friends). $\endgroup$ – Gustavo Delfino Jul 10 '18 at 16:42
  • $\begingroup$ I seen these download progress messages while pulling example data, e. g. ExampleData[{"Audio", "Bird"}]. The datum is cached then, so it occurs only once per datum. The quantity somehow caused a very similar behavior, apparently pulling a paclet. And my quantity was the most regular temporal seconds, nothing non-trivial. No idea if quantities displayed at all before that; MMA had been installed on that machine afresh just for a couple hours. So you did not see that, but a full restart of the whole rig helped. Looks like quantities break in different ways to different people. :( $\endgroup$ – kkm Jul 10 '18 at 17:02

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