Question

If $X=28+(1\times 2\times 3\times 4\times .....\times 16\times 28)$ and $Y=17+(1\times 2\times 3\times ......\times 17)$ then $X-Y$ is a

• A. Prime
• B. Composite
• C. $1$
• D. $0$

Answer 1

Answer: (B)

Composite

$X=28+(1\times 2\times 3\times ....\times 16\times 28)$

$Y=17+(1\times 2\times 3\times ....\times 16\times 17)$

$X-Y=(28-17)+(1\times 2\times 3\times 4\times ....\times 16)\times (28-17)$

$=11\times (1+1\times 2\times 3\times 4\times ....\times 16)$

$\Rightarrow X-Y$ is a composite number