Divisibility Rules: Is Every Multiple of 3 Also a Multiple of 6?

Divisibility Rules with Multiple Conditions

Will a number divisible by 3 necessarily be divisible by 6?

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Step-by-step video solution

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00:00 Is every number divisible by 3 also divisible by 6?
00:04 Let's take an example of a number divisible by 3
00:10 We can see that this number is not divisible by 6
00:14 Therefore, not every number divisible by 3 is divisible by 6
00:18 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

Will a number divisible by 3 necessarily be divisible by 6?

2

Step-by-step solution

To determine if a number divisible by 3 is necessarily divisible by 6, we must apply the divisibility rules for both 3 and 6:

  • A number is divisible by 3 if the sum of its digits is divisible by 3.
  • A number is divisible by 6 if it is divisible by both 2 and 3. Thus, it must also be an even number.

To explore this question, let's consider a counterexample:

Take the number 9 9 . The sum of its digits is 9 9 , which is divisible by 3, so 9 is divisible by 3.

However, 9 is not even, so it is not divisible by 2. As a result, 9 is not divisible by 6 (because it does not satisfy the requirement to be divisible by both 2 and 3).

This counterexample demonstrates that a number divisible by 3 is not necessarily divisible by 6.

Therefore, the statement is incorrect, and the answer is No.

3

Final Answer

No

Key Points to Remember

Essential concepts to master this topic
  • Rule: For divisibility by 6, check both divisibility by 2 and 3
  • Technique: Test counterexample: 9 is divisible by 3 but not 6
  • Check: Even numbers divisible by 3 are always divisible by 6 ✓

Common Mistakes

Avoid these frequent errors
  • Assuming divisibility by 3 automatically means divisibility by 6
    Don't think that 3 divides 6 so all multiples of 3 are multiples of 6 = wrong logic! This ignores that 6 = 2 × 3, so you need BOTH factors. Always check if the number is even AND divisible by 3.

Practice Quiz

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Will a number divisible by 6 necessarily be divisible by 3?

FAQ

Everything you need to know about this question

Why isn't every multiple of 3 also a multiple of 6?

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Because 6 = 2 × 3, a number must be divisible by BOTH 2 and 3 to be divisible by 6. Numbers like 9, 15, 21 are divisible by 3 but not even, so they're not divisible by 6.

How do I quickly check if a number is divisible by 6?

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Use the two-step test: First, is it even? Second, do its digits add up to a multiple of 3? Both must be true for divisibility by 6!

Can you give me examples of numbers divisible by 6?

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Sure! Try 12, 18, 24, 30, 36. Notice they're all even AND their digit sums (like 1+2=3, 1+8=9) are multiples of 3.

What about odd multiples of 3?

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Odd multiples of 3 like 9, 15, 21, 27 can never be divisible by 6 because they fail the "divisible by 2" requirement. They're missing the factor of 2!

Is there a pattern I can remember?

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Yes! Every other multiple of 3 is divisible by 6. The pattern goes: 3 (no), 6 (yes), 9 (no), 12 (yes), 15 (no), 18 (yes)...

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