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Numerical Ability
Log and Antilog
a drawer holds 4 red hats n 4 blue hats. what is the probability of getting exactly 3 red hats or exactly 3 blue hats when taking out 4 hats randomnly out of the drawer n immediatly returning evry hat to the drawer b4 taking out the next!??
1/2
1/8
1/4
3/8
Read Solution (Total 5)
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- suppose there are 4 red balls r1,r2,r3 and r4 and there are 4 blue balls b1,b2,b3 and b4
so total arrangements are 16
now if we take only 3 red balls and 1 blue balls,then there are total 4 arrangements
and same for in case of blue here are total 4 arrangements,so total are 8 arrangements
probability of getting exactly 3 red hats or exactly 3 blue hats when taking out 4 hats randomnly out of the drawer n immediatly returning evry hat to the drawer b4 taking out the next is 8/16=1/2(ans)
- 12 years agoHelpfull: Yes(19) No(4)
- The order is also important here. RRRB or BBBR.
RRRB has 4 possible arrangements and BBBR too. So a total of 8 arrangements. For each of these arrangements p=1/16 so
Ans = 8/16 = 1/2 - 12 years agoHelpfull: Yes(3) No(4)
- (4c1/8c1)*(4c1/8c1)*(4c1/8c1)*(8c1/8c1)
=1/8 - 9 years agoHelpfull: Yes(3) No(2)
- (r,r,r,b)+(r,b,r,r)+(r,r,b,,r)+(b,r,r,r,)
hence 4/8 is ans
=1/2 - 12 years agoHelpfull: Yes(2) No(7)
- 1/2 is ans
- 12 years agoHelpfull: Yes(1) No(9)
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