90
Review: angles, rectangles and area
Textbook: Part 3, pp. 28–29
GoalReview shapes, angles, perimeter and area.
New words
perimeter · perimetrarea · yuzacute angle · o‘tkir burchaksquare centimetre · kvadrat santimetr
Explanation
Let us recall: the perimeter is the sum of the sides and the area is the space a shape covers. All angles of a rectangle and a square are right angles. 1 dm² = 100 cm² and 1 m² = 100 dm². We find the area of a shape by counting square centimetres.
Worked examples
A ticket with sides 9 cm and 6 cm has 6 rows of 9 cm², so its area is 9 + 9 + 9 + 9 + 9 + 9 = 54 cm².
A stage 13 m by 9 m has perimeter 13 + 9 + 13 + 9 = 44 m.
Class activity
“Area and perimeter contest”: two teams get a rectangle card each. One finds the perimeter, the other finds the area by counting squares, and they score points.
Practice
1
A festival ticket is a 9 cm by 6 cm rectangle. What is its area in cm²? (6 rows of 9 cm²)
54
2
A stage has sides 13 m and 9 m. What is its perimeter in metres?
44
3
4 m² 20 dm² + 3 m² 50 dm² = ? dm²
770
4
Calculate: (500 − 235) + 168 = ?
433
5
What is an angle narrower than a right angle called?
An acute angle