So I was doing this problem here and I looked in the back to check my answer, and well... I'll just start off with the problem...

"In water conservation, chemists spread a thin film of certain inert material over the surface of water to cut down the rate of evaporation of water in reservoirs. This technology was pioneered by Benjamin Franklin three centuries ago. Franklin found that 0.10 mL of oil could spread over the surface of water of about 40 m^2 in area. Assuming that the oil forms a monolayer, that is, a layer that is only one molecule thick, estimate the length of each oil molecule in nanometers. (1 nm = 1x10^-9 m)"

I attempted the problem and got 2.5 x 10^1 nm, but the answer in the back of the book is 2.5 nm.

My first attempt:

0.10 cm^3/100 cm*(.10 cm^2/40 m^2)/100 cm/1x10^-9 m

My second attempt involved converting everything to meters, but once again, I had the same answer

I apologize for the obvious stupidity of this post