A tube has an outer diameter of 5 inches and a wall thickness of 0.5 inches. What is the inside diameter?

A tube has an outer diameter of 5 inches and a wall thickness of 0.5 inches. What is the inside diameter?

• A. 4.0 inches
• B. 3.5 inches
• C. 4.5 inches
• D. 5.0 inches

Answer: (A)

When a tube has wall material on both sides, the inner diameter is the outer diameter minus twice the wall thickness. That’s because you subtract the wall thickness from each side. Here, the outer diameter is 5 inches and the wall thickness is 0.5 inches. Subtract 2 × 0.5 = 1 inch from the outer diameter: 5 − 1 = 4 inches. So the inside diameter is 4.0 inches. This aligns with subtracting the wall from both sides; subtracting only once or not at all would give incorrect results.

When a tube has wall material on both sides, the inner diameter is the outer diameter minus twice the wall thickness. That’s because you subtract the wall thickness from each side.

Here, the outer diameter is 5 inches and the wall thickness is 0.5 inches. Subtract 2 × 0.5 = 1 inch from the outer diameter: 5 − 1 = 4 inches. So the inside diameter is 4.0 inches. This aligns with subtracting the wall from both sides; subtracting only once or not at all would give incorrect results.