Q.

The LCM of two prime numbers p and q (p>q) is 221. Find the value of 3p−q.

1 4  
2 28  
3 38  
4 48  

Ans.

(3)

p and q (p > q) are prime numbers, HCF (p,q) = 1

Given, LCM (p,q) = 221

⇒LCM (p,q)×HCF (p,q)=p×q⇒1×221=p×q⇒p×q=221So,  p=17,q=13(∵p>q)3p−q=3×17−13=51−13=38