A drawer has 4 red hats and 4 blue hats. Find the probability of getting exactly 3 red hats or exactly 3 blue hats when taking out 4 hats randomly out of the drawer and immediately returning every hat to the drawer before taking out the next?
option
a)1/2
b)1/4
c)1/8
d)none of these

• i think ans is 1/8
  selecting a red hat can be done in 4c1/8c1 ways=1/2
  it is asked that 3 red or 3 blue (rrrb)or (bbbr)
  (1/2.1/2.1/2.1/2)+(1/2.1/2.1/2.1/2)=1/16+1/16=1/8
• 11 years agoHelpfull: Yes(34) No(7)
• 
  Probablity of taking out a particular color hat = 4/8 = 1/2
  
  P(BBBR) = (1/2)^4
  P(BBRB) = (1/2)^4
  P(BRBB) = (1/2)^4
  P(RBBB) = (1/2)^4
  total = 4 * (1/2)^4
  
  similary for (RRRB) = 4 * (1/2)4
  
  answer = 8 * (1/2) ^4 = 1/2
• 11 years agoHelpfull: Yes(20) No(1)
• ans is 1/2 bcz there are total of 8 cases of getting exactly 3 red or exactly 3 blue so we will have 8*(4/8)*(4/8)*(4/8)*(4/8)=1/2
• 11 years agoHelpfull: Yes(2) No(0)
• 2*(4/8*4/8*4/8*4/8)=1/8
• 11 years agoHelpfull: Yes(1) No(1)
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• 11 years agoHelpfull: Yes(1) No(0)
• 4c3*4c1*2/4^4=1/8
• 11 years agoHelpfull: Yes(1) No(0)
• ans is 1/8
• 11 years agoHelpfull: Yes(0) No(0)