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I'm trying to get into Biology, reading introductory texts. A discussion on E.Coli estimates the mass of the cell from $$density =1g/mL=1g/cm^3$$ and $$volume=1µm^3$$ From this I get $$ mass=density × volume = \frac {10^{-6} g}{10^{-2}}=10^{-4} g$$ which is wrong since the answer is supposed to be $1pg$. What am I doing wrong? Thanks!

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Its simple:

Mass = Density * Volume

= 10^3 (Kg/m3) * (10^-18 m3)

= 10^-15 Kg

which is equal to 10^-12 gram or 1pico gram

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  • $\begingroup$ Wiki gives me micrometers to be $10^{-6}m$. And also that an $mL=cm^3$. Since I don't come from a background where units were ever used, can u please elaborate on how u got ur density and volume compared to mine? Thanks $\endgroup$
    – Mike
    Jun 7, 2016 at 1:16
  • $\begingroup$ @Craig Yes micrometers are indeed 10^-6 meters. But 1 micrometer^3 = (10^-6)^3 = 10^-18 $\endgroup$ Jun 7, 2016 at 2:42
  • $\begingroup$ 10^-18 is in m3 $\endgroup$ Jun 7, 2016 at 2:43
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    $\begingroup$ Ahh... I should've paid attention in high school physics $\endgroup$
    – Mike
    Jun 7, 2016 at 3:44

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