Use dimensional analysis to convert 840 mL to L

 " 0.85 L " ; or, write as:  " L " .

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Step-by-step explanation:

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Note the exact conversion:  1000 mL = 1 L  .

840 mL *  =  ? L  ;

The unit of "mL" cancel out; since "mL/mL" = 1 ;

since any non-zero value, divided by itself, results in "1 " ;

 and we have:

   (840/ 1000) L ;

Cancel out a  "zero" for both the number and the denominator:

to get:

  (84/ 100) L ;  

   84 ÷ 100 = 0.84 ;

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The answer is:  0.84 mL ;

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84/100 = ? ; divide each side by "4" ;

 (84÷4)/(100÷4) = 21/25 ;

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The answer is:  0.85 L ; or, write as:  " L " .

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Hope this is helpful to you.  Best of luck!

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40 is the final : )