NCERT Class XII Mathematics Chapter - - Solutions
© examsnet.com
Question : 92
Total: 101
How many times must a man toss a fair coin so that the probability of having at least one head is more than 90% ?
Solution:
Let the coin be tossed n times.
p be probability of getting a head=
q be probability of getting no head= 1 −
=
P (at least one head) = P(X ≥ 1) = 1 – P(X = 0)
= 1 − n C 0 q n p 0
= 1 − 1 × (
) n × 1 = 1 − (
) n
According to question,1 − (
) n >
⇒ n ≥ 4.
p be probability of getting a head
q be probability of getting no head
P (at least one head) = P(X ≥ 1) = 1 – P(X = 0)
According to question,
© examsnet.com
Go to Question: