A class consists of 15 biology students and 10 chemistry students. If you pick two students at the same time, what's the probability that one is maths and one is chemistry ?  Select the correct option:
A) 2/7  B) 5/7  C) 1/2  D) 3/7  E) 1/2
P(1st b, 2nd c) = 15/25*10/24 = 150/600 = 1/4;   P(1st c, 2nd b ) = 10/25*15/24 = 150/600 = 1/4.   P = 1/4 + 1/4 = 1/2.   Answer: 1/2.
<result>C</result>
A class consists of 15 biology students and 10 chemistry students. If you pick two students at the same time, what's the probability that one is maths and one is chemistry ?