Question

Which of the following is a prime number. A. 12 B. 7 C. 9 D. 4

Answer 1

7 is the correct answer because its only factors are 1 and 7.

If a number have only two factors: 1 and the number itself, then the number is a prime number.

If it has more than 2 factors, then it is a composite number

Hope this helps :)

Answer 2

$\textbf{ \underline { \underline{PRIME NUMBER}}}$


$\text{The \: number \: which \: is \: only \: divisible } \\ \text{by \: one \: and \: itself \: is \: known \: as} \\ \text{prime \: number..}$


$\textbf{ \underline{According to question}}$

$\textsf{(A)} \: \: 12$

$\text{12 \: will \: be \: divisible \: by....} \\ \implies \: 12 = 1,2,3,4,6,12 \\ \\ \implies \text{so , \: 12 \: is \: not \: a \: prime \: number}$


$\textsf{(B)} \: \: 7$

$\text{7 \: will \: be \: divisible \: by....} \\ \implies \: 7 = 1,7\\ \\ \implies \text{so , \: 7\: is \: a \: prime \: number}$


$\textsf{(C)} \: \: 9$

$\text{9 \: will \: be \: divisible \: by....} \\ \implies \: 9 = 1,3,9 \\ \\ \implies \text{so , \: 9 \: is \: not \: a \: prime \: number}$


$\textsf{(D)} \: \: 4$

$\text{4 \: will \: be \: divisible \: by....} \\ \implies \: 4 = 1,2,4\\ \\ \implies \text{so , \: 4 \: is \: not \: a \: prime \: number}$


$\textbf{option \: (b) \: is \: correct} \\ \textbf{7 \: is \: a \: prime \: number...}$