BITSAT2017MathematicsProbabilityActual
A coin is tossed 7 times. Each time a man calls head. The probability that he wins the toss at least four times is
Options
- A1 4
- B5 8
- C1 2
- D1 6
Correct answer
C. 1 2
Step-by-step solution
The man has to win atleast 4 times. ∴ Required probability = C 4 7 1 2 4 1 2 3 + C 5 7 1 2 5 1 2 2 + C 6 7 1 2 6 1 2 + C 7 7 1 2 7 = C 4 7 + C 5 7 + C 6 7 + C 7 7 × 1 2 7 = 64 2 7 = 1 2