106
Dividing by 4
Textbook: Part 3, lesson 100, pp. 60–61
GoalDivide by 4; find an unknown factor.
New words
dividing by 4 · 4 ga bo‘lishunknown factor · noma’lum ko‘paytuvchibracket · qavsquotient · bo‘linma
Explanation
12 : 4 = 3, because 3 × 4 = 12. To find an unknown factor we divide the product by the known factor: if x × 4 = 28 then x = 28 : 4 = 7. In expressions with brackets we calculate inside the brackets first, and division is done before addition and subtraction.
Worked examples
If 12 people form groups of 4, there are 12 : 4 = 3 groups.
(30 + 10) : 4 = 40 : 4 = 10.
Class activity
“Form groups”: the class forms groups of 4. The teacher calls different numbers of children and they write the number of groups as an expression.
Practice
1
12 people were split into groups of 4 for a community work day. How many groups were made?
3
2
36 : 4 = ?
9
3
A square has perimeter 20 cm. How many cm is its side?
5
4
Solve: x × 4 = 28. x = ?
7
5
Calculate: 25 − (16 : 4) = ?
21