A drawer holds 4 red hats and 4 blue hats. What is the probability of getting exactly three red hats or exactly 3 blue hats while 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. 1/8
C. 1/4
D. None of these

• 1/2 is the answer
  
  p(drawing a red hat) = p(drawing a blue hat) = 4/8 = 1/2
  
  exactly 3 R in 4 draw:
  4 ways
  BRRR
  RBRR
  RRBR
  RRRB
  
  each of these have prob : 1/2 * 1/2 * 1/2 * 1/2 = 1/16
  
  thus p(drawing exactly 3 R hats) = 4 * 1/ 16 = 1/4
  
  similarly, p(drawing exactly 3B hats) = 1/4
  
  p(3 R or 3 B) = 1/4 + 1/4 = 1/2
• 11 years agoHelpfull: Yes(8) No(5)
• 1/2*1/2*1/2*1/2*2=1/8 is the answer !!!
• 11 years agoHelpfull: Yes(7) No(2)
• they said they are taking out 4 hats randomly.so, there is no possibility of taking exactly 3 red or blue hats from the drawer.... i think the answer is
  
  D.None of these
• 11 years agoHelpfull: Yes(0) No(0)