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

Test your knowledge with interactive questions

Determine if the following number is divisible by 3:

\( 352 \)

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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