A very stupid question, calculation problem

[cubejunkies]

0.10 mL of oil can spread over a surface of 40 m^2 of water in a film one molecule thick to prevent the water from evaporating as fast. If one nanometer is 1 x 10^-9 meters, what is the length of one oil molecule in nanometers?

Ok so this is a really stupid question, but I got the correct number, but my decimal is in the wrong place, and I've done the problem over and over and over so there's something wrong in my calculations. The correct answer is 2.5 nanometers, but I always get 25 nanometers. Heres my thought process:

0.10 mL/ 100 cm * 0.10 mL/40 m^2/100 cm/1*10^-9 = 2.5*10^1

This is a really stupid question and I apologize

 

[Borek]

What unit is your answer in?

 

[cubejunkies]

cm*nm/m :( i tried multiplying by (1m/100 cm) again as a fudge factor, bu then it made the answer 2.5*10^-1 obviously so idk

 

[Borek]

It looks to me like you are using conversion factors at random. Try to make it in a systematic way. For example - convert everything to meters (meters, squared meters and cubed meters).

 

[cubejunkies]

okay, and since mL are cm^3 and its a monolayer of oil, could i make it into cm^2 because of that?

 

[Borek]

No, volume and surface are different things.