92
Area of a rectangle
Textbook: Part 3, lesson 86, pp. 32–33
GoalFind the area of a rectangle as length times width.
New words
length · bo‘yiwidth · eniarea · yuzmultiplication · ko‘paytirish
Explanation
A rectangle divided into 1 m squares has the same number of squares in every row. We add 5 + 5 + 5, or briefly 5 × 3. To find the area of a rectangle we multiply the length by the width: S = a × b. The area of a square is its side times itself: 3 × 3 = 9.
Worked examples
A rectangle 5 cm by 6 cm: S = 5 × 6 = 30 cm².
A square with side 4 dm: S = 4 × 4 = 16 dm².
Class activity
“Count the area”: each child draws a rectangle, writes its length and width, finds the area by multiplication and checks by counting squares.
Practice
1
A rectangle is 5 cm long and 2 cm wide. What is its area in cm²?
10
2
A square has side 3 cm. What is its area in cm²?
9
3
A square frame has side 4 dm. What is its area in dm²?
16
4
A rectangle with sides 10 cm and 4 cm: what is its area in cm²?
40
5
What is the area of a square with side 6 cm in cm²? Which is bigger: this square or the 10 cm by 4 cm rectangle?
36 cm²; the rectangle is bigger (40 > 36)