Lesson 9 of 11
The big picture
Show on a big screenEvery question here is two solids joined, with a job to do.
| Idea | Remember | Example |
|---|---|---|
| Two solids | Name each solid. Find the join. | Toy: cone on hemisphere. |
| Outside or inside | Area counts squares. Volume counts cubes. | 5082 and 32340. |
| The join | Touching parts are inside. | 7854 − 2772 = 5082. |
| The tent | Canvas, floor and air differ. | 990, 154, 2772. |
| The hollow | Mouth off, bowl on. | 952 − 154 + 308 = 1106. |
| The slant | On a hemisphere: cone height = total − r. | 49 − 21 = 28, l = 35. |
| The job | List only the faces it counts. | Capsule: 2 domes + wall. |
| Start to finish | Read, split, find, pick, compute. | ₹2541. |
This is Chapter 12, Surface Areas and Volumes. Open its exercises. For each object, name the solids first.
Every number here comes from a made-up object. The method stays the same for real ones.