A box contains 6 white balls and 7 black balls. Two balls are drawn random. What is the probability that both are the same colour?
option
A) 5/13
B) 6/13
C) 7/13
D) 6/7

• Ans: B
  The total no of combinations to get 2 balls= 13c2
  The total no of combinations of getting 2 balls of same colour=6c2+7c2
  so, the probability is (6c2+7c2)/13c2
  i.e. (15+21)/78 = 6/13
• 11 years agoHelpfull: Yes(5) No(0)
• There are two ways of of getting both same colour,i.e both white or both black.
  So when we get both black, probabilty is (7/13)*(6/12)=42/156.
  When we get both white, probavility is (6/13)*(5/12)=30/156.
  So total probability of getting both same colour is (42/156)+(30/156)=6/13.
• 11 years agoHelpfull: Yes(0) No(0)