Width measurements and conversions

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

a. How wide is the gap between tiles in centimeters?
b. How wide is the gap in inches
c. How many algae-thicknesses is the gap between tiles


2. Relevant equations



3. The attempt at a solution

First off, I just want to know if I did a and b correctly. To set up a, I took 0.90 mm x 2 to get 1.8 mm per gap. I then converted 1.8 millimeters in order to get to centimeters. I came up with 0.18 centimeters. For b, I just divided 0.18cm/2.54cm to get the answer in inches. As for c, I suppose I will just convert, what do you think about a and b so far?

 

Couldn't I just convert 9.45 micrometers to centimeters and divide by 0.18 cm to get the thickness between the gaps in terms of algae thicknesses?

 

So I converted 0.18 centimeters to micrometers and got 1800 micrometers. So then, I just take 1800 micrometers divded by 9.45 micrometers to get how many will fit across? 1800/9.45. I came up with 190.476, but since I can only have two significant figures in my answer, it would be 190 algae cells. How does that sound?