A cylindrical piece of iron pipe is shown below. The wall of the pipe is 1.25 inch thick:

The figure shows a cylinder of height 16 inches and diameter 6 inches.

What is the approximate inside volume of the pipe? (4 points)

88 cubic inches

49 cubic inches

142 cubic inches

154 cubic inches

1 answer

To find the approximate inside volume of the cylindrical pipe, we first need to determine the dimensions of the inner cylinder (the hollow part) after accounting for the wall thickness.

  1. Outer Dimensions:

    • Height (h) = 16 inches
    • Outer diameter = 6 inches
    • Outer radius (R) = Outer diameter / 2 = 6 inches / 2 = 3 inches
  2. Inner Dimensions:

    • The wall thickness is 1.25 inches, so we subtract twice the wall thickness from the outer diameter to find the inner diameter.
    • Inner diameter = Outer diameter - 2 × wall thickness = 6 inches - 2 × 1.25 inches = 6 inches - 2.5 inches = 3.5 inches
    • Inner radius (r) = Inner diameter / 2 = 3.5 inches / 2 = 1.75 inches
  3. Calculating Inner Volume: The volume \( V \) of a cylinder is calculated using the formula: \[ V = \pi r^2 h \] where \( r \) is the inner radius and \( h \) is the height.

  4. Substituting the Values: \[ V = \pi (1.75)^2 (16) \] \[ V = \pi (3.0625) (16) \] \[ V = \pi (48.99999999) \] \[ V \approx 3.14159 \times 49 \approx 154.2 \text{ cubic inches} \]

Therefore, the approximate inside volume of the pipe is 154 cubic inches.