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Question: Answered & Verified by Expert
A box contains 3 coins B1,B2,B3 and the probability of getting heads on the coins are 12,14,18 respectively. If one of the coins is selected at random and tossed for 3 times and exactly 3 heads appeared, then the probability that it was coin B1 is
MathematicsProbabilityJEE Main
Options:
  • A 973
  • B 1073
  • C 3673
  • D 6473
Solution:
1942 Upvotes Verified Answer
The correct answer is: 6473
A selected coin got exactly 3 heads
B1 coin B1 is selected
B2 coin B2 is selected
B3 coin B3 is selected
PB1=PB2=PB3=13
Using Bayes Theorem,
P B 1 A = P A B 1 P A = P B 1 P A B 1 P B 1 P A B 1 +P B 2 P A B 2 +P B 3 P A B 3
=13×12313×123+13×143+13183=6464+8+1=6473

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