A drawer holds 4 red hats and 4 blue hats what is probability of getting exactly three blue hats when

1/4

out of possible 16 outcomes, 4 are desired ones in which we are getting exactly three blue hats when taking out 4 hats randomly out of the drawer and immediately returning every has to the drawer before taking out the next.
these combinations are
BBBR
BBRB
BRBB
RBBB

so prob = 4/16 =1/4
12 years agoHelpfull: Yes(13) No(15)
I m not sure about my solution.... if right plz give feed back...
here we have total 8 hat so its total combination is = 8c4
and here three blue hat have to take so remaining 1 hat can be red ..
so for blue hat =4c3
red hat=4c1
probability=event occurance/total possible value
probability=4c3*4c1/8c4
s0 approximate ans is 1/4
12 years agoHelpfull: Yes(6) No(16)
there are tottal 8 hats
we will totaly select 4 from 8
and 3 from 4 blue hats
and 1 from 4 red hat
so as per product rule
(3/4*1/4)/(4/8)=3/4*1/4*2=3/4*1/2=3/8
12 years agoHelpfull: Yes(3) No(11)
@KRISHNAMURTHY ,, kindly explain how is it 1/2 ?
12 years agoHelpfull: Yes(3) No(2)
let red hat is success , prob of success is 4/8 = 1/2
for first case 3 red hat - 4C3(1/2)^3(1/2) since nCr(succ)^r(failure)^(n-r)
failure= 1- succ
similarly for second case 4C3(1/2)^3(1/2)
add both case 2*4C3(1/2)^3(1/2) = 2*4*1/16 =1/2
12 years agoHelpfull: Yes(1) No(6)

A drawer holds 4 red hats and 4 blue hats. what is probability of getting exactly three blue hats when taking out 4 hats randomly out of the drawer and immediately returning every has to the drawer before taking out the next?
a)1/2
b)1/8
c)1/4
d)3/8