Three prime numbers p, q and r, each less than 20, are such that p - q = q - r. How many distinct possible values can we get for (p + q + r) ?
A
4
B
5
C
6
D
More than 6
Correct Answer: Option A
Explanation
1. **Analyze Structure**: The condition $p - q = q - r$ means $p, q, r$ are in Arithmetic Progression (AP). Thus, $p + r = 2q$. The sum required is $p + q + r = 3q$. This means the number of distinct sums is exactl