81
Rectangle and square
Textbook: Part 3, lesson 76, pp. 10–11
GoalDefine and tell apart a rectangle and a square.
New words
quadrilateral · to‘rtburchakrectangle · to‘g‘ri to‘rtburchaksquare · kvadratside · tomon
Explanation
A rectangle is a quadrilateral whose angles are all right angles. A square is a rectangle whose sides are all equal. So every square is a rectangle, but not every rectangle is a square. We name a shape by the letters at its corners: ABCD.
Worked examples
ABCD is a rectangle and KLMN is a square. A notebook page is a rectangle, a chess square is a square.
If a square has side 5 cm, its perimeter is 5 + 5 + 5 + 5 = 20 cm.
Class activity
“Shape search”: children cut rectangles and squares from coloured paper. They measure the sides with a ruler to find out which ones are squares.
Practice
1
How many sides does a square have, and how are they related?
4, all equal
2
Is every rectangle a square?
No
3
A flag is 80 cm long and 30 cm narrower than long. What is its perimeter in cm?
260
4
A square has side 6 cm. What is its perimeter in cm?
24