1
Pattern rules
Discover Mathematics P2: Term 2, Lessons 71–80
GoalFind the rule of a number pattern and write the next numbers.
New words
pattern · numbers that follow a rule again and againrule · what we do to get from one number to the nextnext · the number that comes after
Explanation
A number pattern follows a rule. To find the rule, look at how much each number goes up. In 10, 15, 20, 25 each number is 5 more than the one before, so the rule is plus 5, written +5. Then the next numbers are 30 and 35. Always check the rule on every pair of numbers, not only the first pair. Patterns can count by 2s, 3s, 4s, 5s, 10s and more. A number line helps: each jump is one step of the rule.
Worked examples
3, 6, 9, 12: each number is 3 more. The rule is +3. Next: 15, 18.
20, 30, 40, 50: the rule is +10. Next: 60, 70.
5, 7, 9, 11: the rule is +2. Next: 13, 15. These are all odd numbers.
Class activity
Skip counting walk. Make a number path with chalk or paper squares numbered 0 to 30. Hop along it by 2s, then 3s, then 5s. Say each number loudly. Write the numbers you landed on and the rule.
Practice
1
Write the next two numbers: 0, 3, 6, 9, __, __
The rule is +3. Next: 12, 15.
2
Write the next two numbers: 10, 15, 20, 25, __, __
The rule is +5. Next: 30, 35.
3
What is the rule of 4, 8, 12, 16?
+4, because each number is 4 more.
4
Complete the pattern: 20, 40, 60, 80, __, __. What is the rule?
The rule is +20. Next: 100, 120.
5
Karim wrote 2, 4, 6, 9, 10 with the rule +2. Which number is wrong?
9 is wrong. After 6 comes 8.