140
Multiplying and dividing by 10 and 100
Textbook: Part 4, lesson 130, pp. 32–33
GoalKnow how to multiply and divide by 10 and by 100.
New words
round number (ending in 0) · yaxlit sonzero · nolmultiplying by 10 · 10 ga ko‘paytirishdividing by 100 · 100 ga bo‘lish
Explanation
To multiply a number by 10 we write one zero on its right: 7 × 10 = 70. To multiply by 100 we write two zeros: 7 × 100 = 700. Swapping factors works here too: 10 × 7 = 7 × 10. To divide a round number by 10 we remove one zero, by 100 two zeros: 80 : 10 = 8, 600 : 100 = 6. Multiplication and division are opposites: 5 × 10 = 50, 50 : 10 = 5.
Worked examples
100 × 3 = 100 + 100 + 100 = 300.
7 × 100 = 700 and 700 : 100 = 7.
Class activity
“Add a zero – take a zero”: children hold digit cards and “0” cards. When the teacher says “× 10” or “: 10”, a child with a zero card joins or leaves the line.
Practice
1
7 × 10 = ?
70
2
3 × 100 = ?
300
3
80 : 10 = ?
8
4
600 : 100 = ?
6
5
10 rows of 30 tiles were laid on a library path. How many tiles were needed in all?
300