Math Problem Statement

Find the volume (in cm3) of the figure. Round to the nearest hundredth of a unit. A rectangular solid has a small piece missing in its bottom half. The edge between the top face and the back face is 4 cm. The edge between the right face and the back face is 4 cm. The edge between the right face and the bottom face is 8 cm. A half-circle is cut out of the front face with its flat part, which measures 2 cm, along the bottom edge of the face. The space cut out from this half-circle continues straight through the block, such that another half-circle is cut out from the back face, and the space between is empty.

Solution

To find the volume of the given rectangular solid with a missing half-cylinder, let's break down the problem into steps:

Step 1: Find the volume of the full rectangular solid.

The dimensions of the rectangular solid can be inferred from the description:

  • The edge between the top face and the back face is the height, h=4cmh = 4 \, \text{cm}.
  • The edge between the right face and the back face is the width, w=4cmw = 4 \, \text{cm}.
  • The edge between the right face and the bottom face is the length, l=8cml = 8 \, \text{cm}.

The volume of the full rectangular solid without the missing piece is calculated using the formula for the volume of a rectangular prism: Vrectangular=l×w×hV_{\text{rectangular}} = l \times w \times h Vrectangular=8cm×4cm×4cm=128cm3V_{\text{rectangular}} = 8 \, \text{cm} \times 4 \, \text{cm} \times 4 \, \text{cm} = 128 \, \text{cm}^3

Step 2: Find the volume of the missing half-cylinder.

  • The diameter of the half-circle cut out from the front and back face is 2cm2 \, \text{cm}, so the radius of the half-circle is r=22=1cmr = \frac{2}{2} = 1 \, \text{cm}.
  • The length of the half-cylinder is the same as the length of the block, which is l=8cml = 8 \, \text{cm}.

The volume of a full cylinder is given by: Vcylinder=πr2hV_{\text{cylinder}} = \pi r^2 h For the half-cylinder, the volume is half that of a full cylinder: Vhalf-cylinder=12×πr2lV_{\text{half-cylinder}} = \frac{1}{2} \times \pi r^2 l Substitute the known values: Vhalf-cylinder=12×π×(1cm)2×8cmV_{\text{half-cylinder}} = \frac{1}{2} \times \pi \times (1 \, \text{cm})^2 \times 8 \, \text{cm} Vhalf-cylinder=12×π×8=4πcm3V_{\text{half-cylinder}} = \frac{1}{2} \times \pi \times 8 = 4\pi \, \text{cm}^3 Vhalf-cylinder4×3.1416=12.57cm3V_{\text{half-cylinder}} \approx 4 \times 3.1416 = 12.57 \, \text{cm}^3

Step 3: Subtract the missing volume from the volume of the full rectangular solid.

Now, subtract the volume of the half-cylinder from the volume of the rectangular solid: Vtotal=VrectangularVhalf-cylinderV_{\text{total}} = V_{\text{rectangular}} - V_{\text{half-cylinder}} Vtotal=128cm312.57cm3=115.43cm3V_{\text{total}} = 128 \, \text{cm}^3 - 12.57 \, \text{cm}^3 = 115.43 \, \text{cm}^3

Final Answer:

The volume of the figure is approximately 115.43cm3115.43 \, \text{cm}^3.


Would you like any further clarification on this? Here are five related questions to deepen understanding:

  1. How would the volume change if the diameter of the cut-out half-cylinder were increased?
  2. How do you find the surface area of this figure?
  3. What is the volume if the cut-out were a full cylinder instead of a half-cylinder?
  4. How do you calculate the volume of a similar figure with an elliptical cut-out?
  5. How does the orientation of the cut-out affect the volume calculation?

Tip: When subtracting volumes, make sure that the removed section's dimensions and position align with the object's total dimensions!

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Math Problem Analysis

Mathematical Concepts

Geometry
Volume
Subtraction of Solids

Formulas

Volume of rectangular prism: V = l × w × h
Volume of cylinder: V = πr^2h
Volume of half-cylinder: V = (1/2) × πr^2h

Theorems

Cylinder Volume Theorem

Suitable Grade Level

Grades 9-11