Question

A bag contains 3 red marbles and 4 blue marbles. Two marbles are drawn at random without replacement. What is the probability they will both be blue?

Answer 1

`P(A)=(C(4,2))/(C(7,2))\\\\ P(A)=((4!)/(2!2!))/((7!)/(2!5!))\\\\ P(A)=(4!)/(2!2!)\cdot(2!5!)/(7!)\\ P(A)=3\cdot4\cdot(1)/(6\cdot7)\\ P(A)=(2)/(7)`