Let A={x|x be a prime no. and x<30}.The no. of different rational nos. whose numerator and denominator belong to A is?

as there are 10 prime no. which are less than 30.so here we have 10 options from which we need 2 numers 1 for numerator and 1 for denominator,so

no. of different rational numbers whose denominator and numerator belongs to A=10 C2

                                                                                                                  =45