We learned about different 3D solids. Identify and list objects or structures around you that are cubical, cuboidal, cylindrical, conical, spherical, or pyramidal in shape, or closely resemble these shapes.
Step-by-step solution
Idea: Look for the defining feature of each solid: six equal square faces (cube), six rectangular faces (cuboid), two equal circles joined by a curved surface (cylinder), a circle narrowing to a point (cone), all points the same distance from a centre (sphere), a flat base narrowing to one apex (pyramid).
- Cubical (6 equal squares): dice, ice cube, sugar cube, a Rubik’s cube. Cuboidal (6 rectangles): brick, book, matchbox, almirah, shoe box, the classroom itself.1 mark
- Cylindrical: LPG cylinder, water pipe, tin can, unsharpened pencil, drum, pillar. Conical: ice-cream cone, funnel, traffic cone, birthday cap, conical tent.1 mark
- Spherical: football, globe, marble, orange, laddoo (and hemispherical: bowl, dome, igloo). Pyramidal: the pyramids of Egypt, pyramid-shaped roofs and tents, a triangular-pyramid puzzle, a tetrahedral milk pack.1 mark
Check: Each object listed has the defining feature of its shape (e.g. a tin can has two equal circular ends joined by a curved surface: a cylinder) ✓.
Answer to write in the exam
Cubical: dice, ice cube, Rubik’s cube
Cuboidal: brick, book, matchbox, almirah
Cylindrical: gas cylinder, pipe, tin can, pillar
Conical: ice-cream cone, funnel, traffic cone, tent
Spherical: ball, globe, marble, orange; hemispherical: bowl, dome
Pyramidal: pyramids of Egypt, pyramid-shaped roofs
Common mistakes that cost marks
- Calling a book or brick a cube. Its faces are rectangles of different sizes, so it is a cuboid.
- Calling a bucket a cylinder without saying ‘approximately’. Its top is wider than its bottom.
- Calling a circle or a disc a sphere. A sphere is solid (3D); a circle is flat.
How this can come in the exam
Which of these is closest in shape to a right circular cone?
- a cricket ball
- a funnel’s top part
- a matchbox
- a water pipe
Show answer
(B) a funnel’s top part
A funnel’s wide part narrows from a circle to a point: a cone. A ball is a sphere, a matchbox a cuboid, a pipe a cylinder.
Try one yourself
Name two objects that are made of two of these shapes joined together.
Show answer
A medicine capsule (cylinder with two hemispheres); an ice-cream cone with a scoop on top (cone with a hemisphere); a temple dome on a cuboid building.
More questions like this
- Activity: Find the approximate volumes of a gas cylinder, a bucket, any cylindrical vessel, a cupboard, a water tank that you can find near you (use 1000 cm3 = 1 litre).
- Lallan’s golgappa (a small hollow ball made of wheat) stall has a cylindrical vessel with pani (spiced water) in it. The vessel is of radius 10 cm and it has pani up to a height of 50 cm. Estimate the number of golgappas he can serve assuming all golgappas are spheres. Before calculating, make a guess.
Can you guess what number this could be — is it in the hundreds, thousands, or more? - Anirban saw a few tennis balls lying around. He wondered, “How many tennis balls can fit in an empty classroom?”. The classroom is of dimensions 30 ft × 30 ft × 15 ft. Estimate how many tennis balls of radius 3 cm fit in this classroom. Before calculating, make a guess.
- Make an estimate based on the second and third configurations.
- Estimate how many scoops of ice cream can be obtained from a cuboidal container of dimensions 10 cm × 15 cm × 20 cm.