UPSC 2014 CDS II Math Paper

p, q, r are prime number such that p<q<r<13.
∴ p can take the values 2,3,5,7,11.
q can take the values 3,5,7,11.
r can take the values 5,7,11.
For , which is not a prime number
For , which is a prime number
For , which is not a prime number
For , which is a prime number
So, there are 2 cases where, p+q+r is also a prime number