Plane — Grade 7 Accelerated, what it means and where it is taught
A perfectly flat surface extending forever.
Taught in Grade 7 Accelerated.
Where it is taught
Practise this idea
3 questions in the course bank use Plane, in Plane Sections of 3-D Figures.
Problem 1
What is the greatest number of sides a cross section of a cube can have?
Worked answer
6
A cube has 6 faces
A plane can be tilted to pass through all six at once
That gives a hexagon — 6 sides.
Problem 2
A single flat cut slices off one corner of a cube. What shape is the new face?
- A square
- A triangle
- A pentagon
- A hexagon
Worked answer
A triangle
Three faces meet at a corner, so the plane crosses three faces
Three faces cut gives a triangle.
Problem 3
A cube is sliced through the diagonal of its top face and the parallel diagonal of its bottom face. What shape is the cross section?
- A square
- A rectangle
- A triangle
- A hexagon
Worked answer
A rectangle
The plane crosses four faces, so the cross section has four sides
All four corners are right angles, but the horizontal sides are diagonals — longer than the vertical edges
So it is a rectangle, not a square.