129
Multiplying and dividing by 1
Textbook: Part 4, lesson 120, pp. 10–11
GoalKnow the rules for multiplying and dividing by 1.
New words
one · birdoes not change · o‘zgarmaydisharing equally · teng bo‘lishequation · tenglama
Explanation
A number times 1 stays the same: a × 1 = 1 × a = a (4 × 1 = 4, one group of four). A number divided by 1 also stays the same: a : 1 = a. A number divided by itself gives 1: 7 : 7 = 1.
Worked examples
9 × 1 = 9 and 9 : 1 = 9.
If 15 × x = 15, then x = 1, because 15 × 1 = 15.
Class activity
“One each”: 9 children each get 1 flag. Children act out “how many flags in all?” (9 × 1) and “9 flags handed out 1 each, how many children?” (9 : 1).
Practice
1
1 × 20 = ?
20
2
49 : 1 = ?
49
3
8 : 8 = ?
1
4
15 × x = 15, x = ?
1
5
At breakfast in a hotel each tourist got 1 cup of tea. 49 cups were served. How many tourists are there?
49