Question

which of these numbers is prime?

choose 1 answer:

a 19

b 56

c 63

d 87

e 93

Explanation:

Define prime and composite numbers

Using the Prime Numbers and Composite Numbers knowledge points
A prime number has exactly two positive factors: 1 and itself. A composite number has more than two factors.

Analyze option A

Using the Prime Numbers knowledge point

$$ \text{Factors of } 19: 1, 19 $$

Since 19 has no other divisors, it is prime.

Analyze option B

Using the Factors and Multiples knowledge point

$$ 56 = 2 \times 28 $$

Since 56 is even and greater than 2, it is composite.

Analyze option C

Using the Factors and Multiples knowledge point

$$ 63 = 3 \times 21 $$

Since 63 has factors other than 1 and itself, it is composite.

Analyze options D and E

Using the Factors and Multiples knowledge point

$$
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$$

Both numbers are divisible by 3, making them composite.

Answer:

• (A) 19 (Correct answer)
• (B) 56
• (C) 63
• (D) 87
• (E) 93