91
What is multiplication?
Textbook: Part 3, lesson 85, pp. 30–31
GoalThe idea of multiplication: a short way to write a sum of equal addends.
New words
multiplication · ko‘paytirishequal addends · bir xil qo‘shiluvchilartimes · martashort notation · qisqa yozuv
Explanation
A short way to write a sum of equal addends was invented: 5 + 5 + 5 + 5 + 5 + 5 = 5 × 6. This new operation is called multiplication. We read “5 × 6” as “5 taken 6 times”. We find the result by adding: 30.
Worked examples
2 + 2 + 2 + 2 + 2 = 2 × 5 = 10.
7 + 7 + 7 = 7 × 3 = 21.
Class activity
“Count in groups”: children split 20 sticks into groups of five and write the addition as multiplication: 5 + 5 + 5 + 5 = 5 × 4.
Practice
1
Write the sum as a product: 7 + 7 + 7 = 7 × ?
3
2
Calculate: 2 × 5 = ?
10
3
Calculate: 8 × 5 = ? (8 + 8 + 8 + 8 + 8)
40
4
Each class has 35 pupils. How many pupils are in 4 classes?
140
5
Put a sign (<, > or =): 50 + 50 + 50 and 50 × 3
=