On one side of a coin there is the number 0 and on the other side the number 1. What is the probability that the sum of three coin tosses will be 2 if a 1 was the value of the first coin flip ?
Choose one
A) 1/8.
B) 1/4.
C) 1/5.
D) 3/8.
E) 1/3.
Assume the coin is unbiased.   Possible sums from 3 tosses = 0,1,2,3   O and 3 are possible in only 1 case each. (0,0,0 or 1,1,1)   1 is possible in 3C1 = 3 cases. (1,0,0; 0,1,0 or 0,0,1) or   similarly, 2 is possible in 3C2=3 cases (1,0,1; 1,1,0; 0,1,1)   If 1 was the first flip you can only have (1,0,0) (1,1,1)(1,0,1) (1,1,0) only two of these have a value of 2   So answer will be 2/8 OR 1/4. Option 1/4..
<result>B</result>
On one side of a coin there is the number 0 and on the other side the number 1. What is the probability that the sum of three coin tosses will be 2 if a 1 was the value of the first coin flip ?