Every Number Serves A Purpose

Number Theory Level 2

The number 5 × A 5 \times A is divisible by 3. Is it true that A must be divisible by 3?

Part 1 Part 3

No, it is not true Yes, it is true

Ronald Chén by Ronald Chén , 32, Guatemala

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2 solutions

Ryan Shi
Nov 8, 2016

Remember Prime Factorisation. Since 5A is divisible by 3, and 5 is not divisible by 3, hence A must have 3 as a prime factor.

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Ronald Chén
Nov 8, 2016

Yes, since the decomposition of 5A contains 3, while the decomposition of 5 does not.

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