Question

The minimum number of times a fair coin must be tossed so that the probability of getting at least one head is at least 0.8 is -

• A. 7
• B. 6
• C. 5
• D. None of these

Answer 1

Answer: (D)

None of these

Answer 2

P (At least 1 head) ³ 0.8 Ž 1 – ⁿC₀ ³ 0.8

1 – 0.8 ³ Ž $\frac { 1 } { 5 }$ ³ n = 3, 4, 5 ……. \ (n)_min = 3