Question:

From one side of a solid cube of side 2 units, a square pyramid of height 1 unit was removed as shown in the image, resulting in a solid with 9 surfaces. If one more pyramid of the same dimensions is removed from another side of the resultant solid, how many surfaces can the new resultant solid have?
From one side of a solid cube of side 2 units, a square pyramid of height 1 unit was removed as shown in the image, resulting in a solid with 9 surfaces.

Updated On: Sep 8, 2025
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The Correct Option is A, C

Solution and Explanation

To solve this question, we need to determine the number of surfaces of the solid when a second pyramid is removed from the cube.

Initially, we have a cube with side length of 2 units, which means:

1. The total number of surfaces of a cube is 6.

After removing the first pyramid from one side of the cube:

  • The pyramid has a square base with the same dimension as the cube’s face (2x2) and a height of 1 unit.
  • Upon removal, 4 triangular faces of the pyramid become exposed.
  • Thus, the original face of the cube where the pyramid was removed is replaced with these 4 triangular faces.
  • As a result, after the first removal, we have an additional triangular face.

This gives a total of 9 surfaces: 5 remaining cube faces + 4 triangular pyramid faces.

When the second pyramid with the same dimensions is removed from another face of the solid, consider:

  • The new pyramid removal exposes 4 more triangular faces on another original cube face.
  • One triangular face from each pyramid will meet at the edge of the cube (since cube's original edge length equals the pyramid base edge length), forming a single surface instead of two separate ones.
  • This results in one less surface compared to if they did not meet.

Counting all surfaces:

  • Originally 6 cube faces
  • Minus 2 cube faces where pyramids are removed = 4
  • Plus 8 triangular faces from two sets of removed pyramids
  • Minus 2 for the meeting edge surfaces = 10 total surfaces

Therefore, the resultant solid after removing the second pyramid will have 10 surfaces.

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