Why is 423 a composite number?
A7 divides it
B9 divides it
C3 divides it
D5 divides it
Answer & Solution
Correct answer: C. 3 divides it
1. The digit sum test settles it.
2. That test is the rule for divisibility by three.
3. Since 3 divides 423, it is composite.
_Source: OpenStax, Contemporary Mathematics, Ch 3 'Real Number Systems and Number Theory'_
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