112
Area of rectangles and squares
Textbook: Part 4, lesson 112, pp. 7–9
GoalFind the area of a rectangle, a square and a right triangle by formula.
New words
area · yuzrectangle · to‘g‘ri to‘rtburchaksquare · kvadratright triangle · to‘g‘ri burchakli uchburchak
Explanation
The area of a rectangle is S = a × b (a is the length, b is the width). The area of a square is S = a × a. A right triangle is half of a rectangle with the same two sides, so S = a × b : 2, where a and b are the two sides that form the right angle. Area is measured in square units: cm², dm², m².
Worked examples
A yard is 12 m long and 8 m wide. S = 12 × 8 = 96 m².
The two sides that form the right angle of a right triangle are 6 cm and 8 cm. S = 6 × 8 : 2 = 24 cm².
Class activity
“Grid area”: draw a rectangle on squared paper, count the squares to find its area, then check with the formula. Cut it along the diagonal and see that each triangle is exactly half.
Practice
1
A wheat field is 150 m long and 60 m wide. What is its area in m²?
9000
2
A square rug has side 15 dm. What is its area in dm²?
225
3
The sides forming the right angle of a right triangle are 10 cm and 12 cm. What is its area in cm²?
60
4
A room has area 84 m² and length 12 m. What is its width in m?
7