# Chem Help!!

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The volume of a red blood cell is about
90.0*10^-12cm^3

Assuming that the red blood cells are spherical, what is the diameter of a red blood cell in millimeters?

• Chem Help!! -

volume of a sphere=90.0 x 10^-12cm^3 =4/3πr^3

Solve for r

r={[(90.0 x 10^-12cm^3)*(3/4)]/π}^1/3

The units that you will get will be in cm, so multiply your answer by 10^-1 to get mm.

• Chem Help!! -

V sphere = (4/3)*pi*r^3
90E-12 = (4/3)*pi*r^3
r^3 = ?
r = ?
diameter = 2*r = ? in cm
Convert to mm.

• Chem Help!! -

Devron, I believe you multiply cm x 10 to convert to mm.

• Chem Help!! -

Typo, 10^1, which is 10.
I apologize. Thank you for catching that for me, and multiply r by 2 afterwards to get the diameter.

• Chem Help!! -

When I converted with Devron method I got
27.8*10^-6mm
When I did it Bob's way I got 27.8*10^-5

is this correct?

• Chem Help!! -

After I multiplied by 2 I got a final answer of 0.000556mm

• Chem Help!! -

volume of a sphere=90.0 x 10^-12cm^3 =4/3πr^3

Solve for r

r={[(90.0 x 10^-12cm^3)*(3/4)]/π}^1/3

The units that you will get will be in cm, so multiply your answer by 10 to get mm, and multiply by 2 afterwards to get the diameter.

The methods that I and Dr. Bob222 both showed you are the same. I calculated 5.56 x10-3 mm, but double check my calculations.

• Chem Help!! -

ok cool thanks for your help

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