<PRE><B>Question 825545</B>
F is a factor;

25*F=16
F=16/25
&#39;
500*25/16=781 cc total volume after adding water.

781-500=281 cc of added water.


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A little more formally,
{{{500*25/(x+500)=16}}}, x does not add any antibiotic but simply dilutes the concentration;
500*25=16(x+500)
500*25=16x+500*16
16x=500*25-500*16
16x=500*9
8x=250*9
4x=125*9
ANSWER:    x=281</PRE>