Math Problem Statement

a pit 7m deep was dug out from the ground. the pit is 6m by 3m at the top and 3m by 2m at the bottom. what is the volume of earth removed in cubic meter

Solution

To find the volume of earth removed from the pit, we need to calculate the volume of the frustum of a trapezoidal prism. The shape of the pit is a frustum because the top and bottom are different rectangular areas.

Formula for the volume of a frustum:

V=13h(A1+A2+A1A2)V = \frac{1}{3} \cdot h \cdot (A_1 + A_2 + \sqrt{A_1 \cdot A_2}) Where:

  • VV is the volume.
  • hh is the height of the frustum (7 meters).
  • A1A_1 and A2A_2 are the areas of the top and bottom faces of the frustum.
  • A1A_1 is the area of the top (6m by 3m).
  • A2A_2 is the area of the bottom (3m by 2m).

Step-by-step calculation:

  1. Area of the top face A1A_1: A1=6×3=18m2A_1 = 6 \times 3 = 18 \, \text{m}^2

  2. Area of the bottom face A2A_2: A2=3×2=6m2A_2 = 3 \times 2 = 6 \, \text{m}^2

  3. Substitute values into the volume formula: V=137(18+6+18×6)V = \frac{1}{3} \cdot 7 \cdot (18 + 6 + \sqrt{18 \times 6}) V=137(18+6+108)V = \frac{1}{3} \cdot 7 \cdot (18 + 6 + \sqrt{108}) V=137(18+6+10.39)V = \frac{1}{3} \cdot 7 \cdot (18 + 6 + 10.39) V=13734.39V = \frac{1}{3} \cdot 7 \cdot 34.39 V=13240.73V = \frac{1}{3} \cdot 240.73 V=80.24m3V = 80.24 \, \text{m}^3

Thus, the volume of the earth removed from the pit is approximately 80.24 cubic meters.


Would you like more details on any part of this solution? Let me know if you have any questions!

Here are 5 related questions:

  1. How would the volume change if the height of the pit were different?
  2. What is the formula for calculating the volume of a cone?
  3. How do you calculate the volume of a cylinder?
  4. Can the frustum formula be applied to irregular shapes?
  5. How would you calculate the surface area of a frustum?

Tip: When calculating volumes for shapes with different top and bottom dimensions, remember to use the frustum formula.

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Math Problem Analysis

Mathematical Concepts

Volume
Frustum of a Trapezoidal Prism
Geometry

Formulas

V = (1/3) * h * (A1 + A2 + √(A1 * A2))

Theorems

Volume of a frustum of a trapezoidal prism

Suitable Grade Level

Grades 9-11