Question

Nine balanced coins are tossed together once. Find probability of getting (1) four heads and (2) at least six heads.

Answer 1

Answer:

63/256

65/256

Step-by-step explanation:

balanced coins has

Probability of head = Probability of Tail = 2

9 balanced coins are tossed together

Probability of 4 heads means

4 Heads &  5 Tails

= ⁹C₄(1/2)⁴ * (1/2)⁵

= 126 * (1/2)⁹

= 126/512

= 63/256

Probability of at least six heads.

6 heads 3 tails  + 7head 2Tails  + 8head 2 tails  + 9 head 0 Tails

= ⁹C₆(1/2)⁶(1/2)³ + ⁹C₇(1/2)⁷(1/2)² + ⁹C₈(1/2)⁸(1/2)¹ + ⁹C₉(1/2)⁹(1/2)⁰

= 84(1/2)⁹ + 36(1/2)⁹ + 9(1/2)⁹ + 1(1/2)⁹

= 130 * (1/2)⁹

= 130/512

= 65/256