1. M.SRINIVASAN, PGT (MATHS)
PROBABILITY
CLASS XII
PREPARED BY
M.SRINIVASAN, PGT (MATHS)
ZIET, MUMBAI

2. A FAIR COIN IS TOSSED UNTIL A HEAD OR FOUR TAILS OCCUR
A FAIR COIN IS TOSSED UNTIL A HEAD OR FOUR TAILS OCCUR. IF X DENOTES THE NUMBER OF TOSSESS OF THE COIN, FIND THE MEAN OF X.
THE SAMPLE SAPCE RELATED TO THE GIVEN EXPERIMENT IS
S = {H, TH, TTH, TTTH, TTTT}
LET X DEONOTE THE NUMBER OF TOSSES
X TAKES VALUES: 1,2,3,4 X 1 2 3 4
P(X)
1/8

3. In an examination, 20 questions of true-false type asked
In an examination, 20 questions of true-false type asked. Suppose a student tosses a fair coin to determine his answer to each question. If the coin falls heads, he answers ‘TRUE’; if it falls tails, he answers ‘FALSE’. Find the probability that he answers at least 12 questions correctly.
n = 20

5. He takes 5 steps forward and 6 steps backward
A man takes a step forward with a probability 0.4 and backwards with probability Find the probability that the end of 11 steps, he is one step away from the starting point.
He takes 5 steps forward and 6 steps backward OR
He takes 6 steps forward and 5 steps backward
n = 11
Required Probability