From a pack, two cards are drawn, the probability that either both are black of both are queen is

• 26c2/52c2+4c2/52c2-2c2/52c2
  bcoz 2 queens are of black cards..which were counted twice.
• 12 years agoHelpfull: Yes(29) No(3)
• total no of cards=52
  no of black cards=26
  no of queens=4
  probability of choosing 2 black cards = 26c2/52c2
  probability of choosing 2 queens = 4c2/52c2
  probability of choosing 1st or 2nd condition = (26c2+4c2)/(52c2)
• 12 years agoHelpfull: Yes(7) No(9)
• 26C2/52C2+4C2/52C2...
• 12 years agoHelpfull: Yes(2) No(7)
• Probability of choosing 2 black cards =(26/52)*(26/52)=1/4
  Probability of choosing queen= (4/52)*(4/52)=1/169
  But first case also contains the condition of selecting 2 queens as the 2 black cards could be 2 queens,thus
  total probability=(1/4)+(1/169)-(1/13), where (1/13) is the conditional probability p(queenblack)=(p(queen intersection black))/p(black)
  
• 12 years agoHelpfull: Yes(0) No(0)