Solids, angles and quadrilaterals · Usually met around P2
Prisms, pyramids and the faces of solids
Two bases: a prism; one base and a point: a pyramid. Named after the base.
How to do it
Method
Two bases: a prism; one base and a point: a pyramid. Named after the base
A prism on a 5-sided base is a 5-sided prism: 5 + 2 = 7 faces
Another way
Face by face
Top, bottom, then round the sides
In full
A prism has two matching bases, top and bottom, and rectangles for its sides; it is named after its base, so a prism on a 5-sided base has 5 side faces and 2 bases, 7 faces in all. A pyramid has one base and triangles for its sides, meeting at a point; a pyramid on a 4-sided base has 4 side faces and 1 base, 5 in all. A cylinder has two flat circles and one curved face; a cone has one flat circle and one curved face. Or count face by face, top and bottom, front and back, left and right, marking each one counted.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
A pyramid on a 5-sided base has □ faces, and a prism on a 5-sided base has □ faces.
Fill in each box
Show the answer and working
Answer: 6，7
Pyramid: 5 sides and 1 base, 6; prism: 5 sides and 2 bases, 7.
Example 2
How many faces do 3 prisms on a 3-sided base have in all?
Show the answer and working
Answer: 15 faces
Each has 3 side faces and 2 bases, 5 faces; 3 of them have 15.
Example 3
A prism on a 6-sided base has rectangles for side faces, 6 of them.
True or false?
Show the answer and working
Answer: True
Each of the base's 6 sides has a side face: 6 of them (the two bases aren't sides).
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