87
Finding area on squared paper
Textbook: Part 3, lesson 82, pp. 22–23
GoalFind the area of a shape on squared paper by counting whole and half squares.
New words
whole square · butun katakhalf square · yarim katakgrid film (transparent grid) · paletkaarea · yuz
Explanation
We count the whole squares inside the shape. We join half squares in pairs: two halves make one whole square. Area = number of whole squares + half the number of half squares. A grid film is a transparent sheet divided into squares that helps to count area quickly.
Worked examples
7 whole and 4 half squares: 7 + 2 = 9 squares.
A rectangle 7 squares long and 3 wide has 7 + 7 + 7 = 21 squares.
Class activity
“Grid film”: children draw squares on tracing paper to make a grid film, put it over pictures and count whole and half squares.
Practice
1
A shape has 9 whole and 6 half squares. What is its area in squares?
12
2
A shape has 5 whole and 2 half squares. What is its area in squares?
6
3
A rectangle is 7 squares long and 3 squares wide. What is its area in squares?
21
4
If x = 450, y = 275, t = 300, then (x + y) − t = ?
425
5
If a = 210 and b = 380, then a + (b − 120) − 45 = ?
425