Mathematics Class 9
Surface Area and Volume
Unroll a box, a tin and a cone, and find what each solid covers and holds.
11 lessons · ~81 min total
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Lessons in this topic
- 0 Start here A roadmap: a box unrolled, a box filled, growth by scale, a tin, a cone, round solids, a canvas tent, and picking the right measure. · 4 min You are here
- 1 Six rectangles laid flat A cuboid's net is six rectangles in three pairs. Add them for the surface area. · 7 min
- 2 What the box holds Stack layers of unit cubes. Volume of a cuboid = l × b × h, in cubic units. · 7 min
- 3 Two counts, two growth stories Multiply every edge by k. The surface area grows by k × k and the volume by k × k × k. · 8 min
- 4 A tin unrolled A tin's label unrolls to a rectangle 2πr long and h tall. Volume is the base times h. · 9 min
- 5 The cone and its slant The slant height is √(r² + h²). Curved surface is πrl. Volume is a third of the cylinder. · 9 min
- 6 Round all the way A sphere has surface 4πr² and volume 4/3 πr³. A hemisphere gains a flat face. · 8 min
- 7 A pyramid of canvas A pyramid holds a third of its box. A wall is a triangle built on the slant height. · 8 min
- 8 Which question, which measure Covering wants square units. Filling wants cubic units. A rope wants a length. Some jobs want both. · 7 min
- 9 The big picture Eight ideas, tied together: a skin question in square units, a filling question in cubic ones. · 6 min
- 10 Track quiz Cheat-sheet table plus a reveal quiz — one question per idea. · 8 min
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