number of particles?

Question

here is my attempt at the question..

1. The problem statement, all variables and given/known data

A typical virus is a packet of protein and DNA (or RNA) and can be spherical in shape. The influenza A virus is a spherical virus that has a diameter of 85 nm. If the volume of saliva coughed onto you by your "friend" with the flu is 0.010 cm3 and 1/109 of that volume consists of viral particles, how many influenza viruses have just landed on you?


2. Relevant equations

V = 4/3 x pie x r^3


3. The attempt at a solution

I'm thinking that I should take half of 85nm which is 42.5nm and plugging it into the volume formula for a spherical. The volume of the whole spherical virus comes out to be 3.21E-5.

3.21E-5 / 0.010cm^3 = .00321

1/10^9 of .00321 = 3.11E-7 particles?

Answer 1

Man, you got a bunch of errors. You got units wrong, and a ratio upside down...

First, a nm is a nanometer or 10^(-9) meters

Once you get the spit volume and the virus volume in the same units, then divide Vspit/Vvir

Then, is that 1/109 or 1/10^9 for the fraction of the spit volume that is virus? Figure that out and use the correct fraction.

Answer 2

none of those solutions apply......each mammal has a different dilution rate....a consensus with an electron microscope will just give one an average !