1
From repeated addition to multiplication
Discover Mathematics P3: Term 1, Lessons 11–20
GoalWrite repeated addition as a multiplication equation and name the factors and the product.
New words
multiplication · finding the total of equal groupsfactor · one of the numbers that you multiplyproduct · the answer to a multiplicationequation · a number sentence with an equals sign
Explanation
Equal groups can be added: 4 + 4 + 4 = 12. When the groups are equal we can write a shorter number sentence with the multiplication sign ×. Three groups of 4 is written 3 × 4 = 12 and is read three times four equals twelve. The numbers 3 and 4 are the factors, and the answer, 12, is the product. The first factor tells how many groups, and the second tells how many are in each group. Drawing circles with dots in them is a good way to see it.
Worked examples
Mina puts 3 flowers in each of 5 vases. Add: 3 + 3 + 3 + 3 + 3 = 15. Write it as 5 × 3 = 15. There are 5 groups of 3, so 5 is the first factor.
Three dice each show 6. Add: 6 + 6 + 6 = 18. As a multiplication: 3 × 6 = 18. The factors are 3 and 6 and the product is 18.
Read 7 × 2 = 14 as seven groups of two. The picture shows 7 groups with 2 stars in each: 2 + 2 + 2 + 2 + 2 + 2 + 2 = 14.
Class activity
Dice and circles. Draw 3 circles on paper. Roll a die once and draw that many dots in each circle. Write the repeated addition and the multiplication equation. Roll again, draw 4 circles and do the same. Play 5 rounds and say the factors and the product each time.
Practice
1
Write a multiplication equation for the picture.
4 × 3 = 12 (4 groups of 3).
2
Write 6 + 6 + 6 + 6 + 6 as a multiplication and find the product.
5 × 6 = 30.
3
Name the factors and the product in 8 × 3 = 24.
The factors are 8 and 3. The product is 24.
4
Write 9 + 9 as a multiplication equation.
2 × 9 = 18.
5
Salma says 3 × 5 means 3 + 5. Is she right?
No. 3 × 5 means 3 groups of 5: 5 + 5 + 5 = 15. But 3 + 5 = 8.