67
Other ways to find area
Textbook: Part 2, lesson 67, pp. 87–89
GoalOther ways to find area: counting, cells and fractions of a shape.
New words
unit of area · yuz birligihalf · yarimone third · uchdan birquarter · chorak
Explanation
Area can also be found with a unit: fill the shape with small items and find how many fit in 1 cm². If 8 rice grains fit in 1 cm² and 40 grains fit in the shape, the area is 40 : 8 = 5 cm². For a shape made of equal cells, area = area of one cell × number of cells. A half is the part after dividing by 2, a third after dividing by 3, a quarter after dividing by 4.
Worked examples
40 grains fit in a shape and 8 grains fit in 1 cm²: area 40 : 8 = 5 cm².
An 8 cm × 3 cm rectangle has area 24 cm²; half is 12 cm², a third is 8 cm², a quarter is 6 cm².
Class activity
“Measure with grains”: groups place a hand outline on squared paper, count full and half squares and find its area roughly.
Practice
1
8 rice grains fit in 1 cm². 56 grains fit in a shape. What is its area in cm²?
7
2
One cell of a honeycomb is 6 cm². The honeycomb has 12 such cells. What is its area in cm²?
72
3
A quarter of a 4 cm × 6 cm rectangle is painted. What is the painted area in cm²?
6
4
9 beans fit in 1 cm². 63 beans fit in a shape. What is its area in cm²?
7
5
On squared paper (each square 1 cm²) a shape covers 14 full squares and 6 half squares. What is its approximate area in cm²?
17