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Unit review
Textbook: Part 3, pp. 84–85
GoalReview: grid (paletka), cuboid and cube, nets, circle and disc, fractions, measures.
New words
grid for measuring area · paletkanet · yoyilmaradius · radiusfraction · ulush
Explanation
Let us review. Area with a grid: full cells + half of the partial cells. A cuboid has 12 edges, four each of length, width and height; total edge length = 4 × (a + b + c). A cube has 12 equal edges: 12 × a. The area of a net is the sum of the areas of all faces. In a circle the diameter is twice the radius. Fraction: 1/n of a number means dividing by n. We calculate with measures after converting to the same unit.
Worked examples
Cuboid: length 9 cm, width 4 cm, height 6 cm. Total edge length 4 × (9 + 4 + 6) = 4 × 19 = 76 cm.
3 t 5 centners = 3 000 kg + 500 kg = 3 500 kg. 3 500 kg − 27 kg = 3 473 kg.
Class activity
“Review relay”: the class forms 4 teams. Stations on the board: total edge length, net area, circle, fraction. Each team solves one task and moves to the next.
Practice
1
A cuboid has length 9 cm, width 4 cm, height 6 cm. What is the total length of all its edges in centimetres?
76
2
Find the total length of all edges of a cube with edge 8 cm (cm).
96
3
A cuboid measures 5 cm, 3 cm and 2 cm. What is the area of its net in square centimetres?
62
4
A circle has diameter 14 cm. What is its radius in centimetres?
7
5
How many kilograms is 3 t 5 centners − 27 kg?
3473
6
Measured with a grid, a shape has 14 full and 6 partial cells. Each cell is 1 m². What is the approximate area of the shape in square metres?
17