2. A stack of paper includes 100 sheets that are each 0.13 millimeters thick and 100 sheets that are each 0.18 millimeters thick. How thick, in millimeters, is the entire

Step 1 ：Given that there are 100 sheets of paper each with a thickness of 0.13 millimeters and 100 sheets of paper each with a thickness of 0.18 millimeters.

Step 2 ：We need to find the total thickness of all the sheets of paper.

Step 3 ：To do this, we multiply the number of sheets of each type by their respective thicknesses: \(100 \times 0.13 = 13\) millimeters and \(100 \times 0.18 = 18\) millimeters.

Step 4 ：We then add these two results together to get the total thickness: \(13 + 18 = 31\) millimeters.

Step 5 ：\(\boxed{31}\) millimeters is the total thickness of all the sheets of paper.