Question

There are 18 mathematics majors and 325 computer science majors at a
college.
a) In how many ways can two representatives be picked so that one is a
mathematics major and the other is a computer science major?

Answer 1

By Combinatorial product rule, two representatives can be picked so that one is a

mathematics major and the other is a computer science major in $18\cdot 325=5,850$ ways.