93
Parts of a circle (fractions)
Textbook: Part 3, lesson 93, pp. 75–77
GoalDivide a whole into equal parts and name the fractions: half, a third, a quarter, a sixth, an eighth.
New words
fraction, part of a whole · ulushhalf · yarimquarter · choraksector · sektor
Explanation
If a whole thing (for example a circle) is cut into equal parts, each part is a fraction of the whole. One of two equal parts is a half, 1/2. One of three equal parts is a third, 1/3. One of four equal parts is a quarter, 1/4. If the parts are not equal, we cannot call them fractions. The bottom number tells into how many equal parts the whole is cut; the top 1 means one part is taken.
Worked examples
A pizza is cut into 8 equal sectors. One sector is one eighth, 1/8, of the pizza. If 3 sectors are taken, 5 sectors are left.
A cake of mass 3 kg 600 g is cut into 12 equal pieces: 3 600 : 12 = 300 g each. If 5 pieces are eaten, 7 are left: 7 × 300 = 2 100 g.
Class activity
“Folding fractions”: children fold a paper circle in half, again into quarters, again into eighths and colour each fraction, saying its name. To cut a circle into sixths, open the compass to the radius, mark 6 points around the circle and join them to the centre.
Practice
1
A pizza is cut into 8 equal pieces. What fraction of the whole is one piece?
1/8
2
A circle is divided into 8 equal sectors and 3 are coloured. How many sectors are not coloured?
5
3
The compass was opened to the radius, points were marked around the circle and joined to the centre. Into how many equal sectors is the circle divided?
6
4
A loaf of mass 2 kg 400 g is cut into 8 equal pieces. How many grams is one piece?
300
5
How many quarters make half of a circle?
2