Incidentally, it's helpful to note that are all prime. Here's the list, grouped in sets of five for easy counting This is not particularly GMAT-like: I am not familiar with any GMAT question which cannot be solved in any shortcut way and which requires writing out a tedious list.
There's really no other way to answer this besides listing all the examples. It helps, of course, to be conversant in the primes from one to 100. My friend, where on earth did you get this question? This is, in many ways, a tedious counting question in which we just have to list out the individual cases. If P represents the number of prime numbers between 1 and 102 then what is the value of P?
