Question

A coin is tossed 9 times. The probability of obtaining at most one head is ______

Options

• `5/512`

• `5/256`

• `1/512`

• `1/256`

Answer 1

A coin is tossed 9 times. The probability of obtaining at most one head is `underline(5/256)`.

Explanation:

Probability of getting bead is p = `1/2`

∴ q = `1 - 1/2 = 1/2`

Also, n = 9

∴ Required probability = P(X ≤ 1)

= `""^9"C"_0(1/2)^9 + ""^9"C"_1(1/2)(1/2)^8`

= `10/2^9 = 5/256`