82
Finding area with a grid (paletka)
Textbook: Part 3, lesson 82, pp. 45–47
GoalEstimate the area of a shape with a grid (paletka): whole squares + half of the partly covered squares.
New words
palette grid · paletkawhole square · to‘la katakpart-covered square · chala katakapproximately · taxminan
Explanation
A paletka is a transparent sheet divided into squares. With it we can estimate the area of any shape. 1) Cover the shape with the grid. 2) Count the squares completely inside the shape. 3) Count the squares partly covered. 4) Add half of the part-covered squares to the whole squares. The result is the area in squares; multiply by the area of one square to get cm². Squared notebook paper works as a grid too.
Worked examples
12 whole squares and 10 part squares: 12 + 10 : 2 = 12 + 5 = 17 squares.
If one square has an area of 4 cm²: 17 × 4 = 68 cm².
Class activity
“Blob area”: children draw a blob on squared paper, count whole and part squares, find the area and compare with a neighbour.
Practice
1
A shape has 24 whole squares and 14 part-covered squares. About how many squares is its area?
31
2
There are 9 whole squares and 12 part squares. About how many squares is the area?
15
3
A leaf on the grid covers 30 whole and 18 part squares, one square is 1 cm². About how many cm² is the leaf’s area?
39
4
A mosaic has 5 rows of 12 tiles. One tile has an area of 10 cm². What is the mosaic’s area in cm²?
600
5
A cloud covers 40 whole and 22 part squares, one square is 4 cm². About how many cm² is its area?
204