100
Dividing by 2
Textbook: Part 3, lesson 94, pp. 48–49
GoalDivide by 2; know that division is the inverse of multiplication.
New words
inverse operation · teskari amalequal groups · teng guruhlarhalving · ikkiga bo‘lishchecking · tekshirish
Explanation
Division is the inverse of multiplication. a : 2 = c means c × 2 = a. For example 14 : 2 = 7, because 7 × 2 = 14. The table for dividing by 2: 2 : 2 = 1, 4 : 2 = 2, 6 : 2 = 3, ... 20 : 2 = 10. Dividing by 2 cuts a number into two equal parts.
Worked examples
If 30 pupils are split into 2 equal groups, each group has 30 : 2 = 15.
Choosing the expression: 10 in each of 2 boxes = 10 × 2; 20 pencils shared between 2 boxes = 20 : 2.
Class activity
“Halve it”: children pick even-numbered cards, split the things into two equal parts (sticks, buttons) and recite the table for dividing by 2.
Practice
1
In a language class 30 pupils are split into 2 equal groups. How many pupils are in a group?
15
2
18 : 2 = ?
9
3
20 pencils were put equally into 2 boxes. Which expression fits: 20 : 2 or 10 × 2? What is the value?
10
4
14 : 2 = ? (check: 7 × 2 = 14)
7
5
In a library each of 8 pupils got 2 new textbooks. How many textbooks in total?
16