Perimeter, area and volume
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Perimeter and area of 2D shapes
- Perimeter is the distance around a shape; area is the space inside.
- Rectangle: A = lw. Triangle: A = \frac{1}{2}bh. Parallelogram: A = bh. Trapezium: A = \frac{1}{2}(a + b)h.
- Circle: circumference C = 2\π r = \π d; area A = \π r2.
- For compound shapes, split into simple parts and add or subtract.
- Use perpendicular height for triangle, parallelogram and trapezium area. Perimeter adds all outside edges; include straight edges when finding a semicircle’s perimeter.
Trapezium: perpendicular height
Volume and surface area of 3D shapes
- Prism: volume = cross-sectional area × length. Cuboid: V = lwh. Cylinder: V = \π r2 h; curved surface area 2\π rh.
- Cone: V = \frac{1}{3}\π r2 h; curved surface area \π r l (slant height l).
- Sphere: V = \frac{4}{3}\π r3; surface area 4\π r2. Pyramid: V = \frac{1}{3} \times \text{base area} \times h.
- For a closed cylinder, add both circular ends: total surface area = 2πr² + 2πrh. A right cone has total surface area πr² + πrl, with slant height l; an open solid omits its missing faces.
- Cylinder and cone formulas here refer to right circular solids. The h in each volume formula is perpendicular height.
Cone: radius and perpendicular height
Units and conversions
- Length: cm, m. Area: cm², m². Volume: cm³, m³. 1 m² = 10 000 cm²; 1 m³ = 1 000 000 cm³; 1 litre = 1000 cm³.
- Always state the correct units.
Perimeter and area
Strategy
- Draw and label diagrams, identify the shape, pick the formula, and substitute carefully, giving the answer in an appropriate form (in terms of \π or to 3 s.f.).
Slide
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Câu hỏi luyện tập
Xem trước miễn phí — 8 trên 32 câu hỏi. Đăng ký để xem tất cả.
1.What is the area of a rectangle 5 cm by 8 cm?
Easy- A13 cm²
- B26 cm²
- C40 cm²
- D80 cm²
2.What is the area of a circle with radius 4 cm? Leave in terms of \π.
Easy- A8\π
- B16\π
- C4\π
- D64\π
3.What is the circumference of a circle with diameter 10 cm (in terms of \π)?
Easy- A10\π cm
- B20\π cm
- C5\π cm
- D100\π cm
4.What is the area of a parallelogram with base 7 cm and perpendicular height 4 cm?
Easy- A28 cm²
- B14 cm²
- C22 cm²
- D11 cm²
5.What is the area of a trapezium with parallel sides 6 cm and 10 cm and perpendicular height 4 cm?
Easy- A32 cm²
- B64 cm²
- C24 cm²
- D40 cm²
6.A semicircle has diameter 10 cm. What is its area in terms of \π?
Easy- A12.5\π cm²
- B25\π cm²
- C50\π cm²
- D5\π cm²
7.What is the volume of a cuboid 2 cm by 3 cm by 5 cm?
Easy- A10 cm³
- B30 cm³
- C31 cm³
- D62 cm³
8.How many cm³ are in 1 litre?
Easy- A10
- B100
- C1000
- D10 000
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