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?