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Class 7

Chapter 6: Number Play

Quick divisibility checks: by 2 if last digit is even; by 3 if sum of digits divisible by 3; by 5 if last digit is 0 or 5; by 9 if sum of digits divisible by 9.

Learning outcomes

  • Investigate divisibility rules
  • Reason about even/odd and prime properties

Activities

  • Divisibility-rule conjecture lab

Worked examples

Read through these first, then try the practice below.

  1. Example 1 — Divisible by 3?

    Is 432 divisible by 3?

    Solution: Sum of digits 4+3+2 = 9, which is divisible by 3. Yes.

  2. Example 2 — Divisible by 9?

    Is 459 divisible by 9?

    Solution: Sum 4+5+9 = 18, which is divisible by 9. Yes.

Self-do practice

Question 1 of 3 · Score 0/0

True or False: 765 is divisible by 5.

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