3
Multiples of 5 and 10
Discover Mathematics P3: Term 1, Lessons 21–30
GoalSkip count by 5 and 10, notice the last digits, and link multiples to multiplication equations.
New words
multiple of 5 · a number you reach by skip counting by 5multiple of 10 · a number you reach by counting by 10; it always ends in 0last digit · the digit in the ones place
Explanation
Count by 5: 5, 10, 15, 20, 25, 30. The multiples of 5 always end in 5 or 0. Count by 10: 10, 20, 30, 40, 50. The multiples of 10 always end in 0. Every multiple of 10 is also a multiple of 5. Each multiple comes from a multiplication fact: 6 × 5 = 30, so 30 is the sixth multiple of 5. For tens, put a zero after the number of tens: 7 × 10 = 70. Counting by 5 and 10 is useful with money. Six notes of 5 LE make 30 LE.
Worked examples
On the chart up to 50, the numbers in one colour are multiples of 5 only: 5, 15, 25, 35, 45. The numbers in the other colour are multiples of 10: 10, 20, 30, 40, 50. All of them are multiples of 5.
Youssef has 6 notes of 5 LE. The tape shows 6 equal parts of 5. 6 × 5 = 30, so he has 30 LE.
The picture shows 7 rods, and each rod is 10. 7 × 10 = 70. Skip count by 10: 10, 20, 30, 40, 50, 60, 70.
Class activity
Pretend shop. Use pretend notes of 5 LE and 10 LE. Make 40 LE in different ways, such as 4 tens, or 8 fives, or 2 tens and 4 fives. Write a multiplication or addition for each way, and check that each one gives 40.
Practice
1
Write the multiples of 5 from 5 to 50.
5, 10, 15, 20, 25, 30, 35, 40, 45, 50.
2
What is 7 × 5?
35.
3
Mostafa has 8 notes of 10 LE. How much money does he have? Write the equation.
8 × 10 = 80 LE.
4
Is 65 a multiple of 5? Is it a multiple of 10?
Yes for 5, because it ends in 5. No for 10, because it does not end in 0.
5
How many tens do the blocks show? Write the multiplication equation.
4 tens: 4 × 10 = 40.