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?

The question asks for how many will fit across. You divide the algae width INTO the gap in the tile dimension. Of course you need to make sure your units are correct, so the gap distance should be in the same units as the algae width.

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?