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I am reading a paper and the dimensions for some electrodes are given, but I was wondering if I was reading it properly:

30 × 15 mm2, is this the same as: (30 × 15)mm2 ?

To track the published paper I provide below its Digital Object Identifier (DOI) commonly used in online research papers. This number should lead you directly to the paper.

DOI: 10.1002/aesr.202000093

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    $\begingroup$ those measurements actually make no sense $\endgroup$
    – jsotola
    Aug 2 at 21:55
  • $\begingroup$ "Both electrodes were cut in dimensions of 30x15mm2." This is word by word what is stated on the article. $\endgroup$
    – RSM
    Aug 2 at 21:57
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    $\begingroup$ 30×15 mm2 may be 30 something long with 15 mm2 cross section .... (30×15) mm2 could just mean 450 mm2 cross section, no stated length $\endgroup$
    – jsotola
    Aug 2 at 22:26
  • $\begingroup$ Yeah, I am not sure how to interpret it either. As you said, it could be interpreted in those two ways. Due to the lack of units on the first number I guessed it meant (30x15)mm2. $\endgroup$
    – RSM
    Aug 2 at 22:43
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    $\begingroup$ Are we all supposed to know what a "DOI" is? (I don't.) There's a hyperlink button on the editor toolbar or you can use the syntax [Link text](http://url.com). $\endgroup$
    – Transistor
    Aug 2 at 22:46
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If you are referring to the article A Structural Battery and its Multifunctional Performance then the dimensions appear to be incorrectly written.

Structural Battery Full Cell Preparation (Section 4)

An illustrative overview of the structural battery composite full cells manufacture is shown in Figure 1. The negative electrode was made from a CF spread tow and the positive electrode was a commercially available LFP electrode foil. Both electrodes were cut in dimensions of 30 × 15 mm2.

I think this is an area of 30 mm × 15 mm = (30 × 15) mm2. Your second version is correct. Theirs is sloppy writing.

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  • $\begingroup$ While the source's writing may be sloppy in the sense of intuition, it is mathematically sound. Units can be treated as algebraic factors and 30 mm × 15 mm = (30 × 15) mm² = 30 × 15 × mm² = 30 × (15 mm²) = 30 × 15 mm². What would actually be mathematically invalid would be an expression such as 30 ± 15 mm, which is not equal to (30 ± 15) mm = 30 mm ± 15 mm. The issue pointed out in this question is not an example of such mathematical mistakes, and only a relatively unfamiliar way of writing the information. I think "incorrect" may be too harsh a word. $\endgroup$ Aug 13 at 19:39

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