Probability

1. In how many different ways can a true-false test consisting of 9 questions be answered ?


2. A pair of dice is tossed. Find the probability of getting
a) a total of 8.
b) at most a total of 5.



Solutions:

1.
True-False  => 2 Options
9C2 = 9! / 2!7! = 36 ways


2.
Sample Space = 6 x 6 =36

a) total of 8 {4+4 , 5+3, 3+5, 6+2, 2+6}
P {a total of 8}
 = 5/36

b) at most 5 { 1+1, 1+2, 1+3, 1+4, 2+1, 2+2, 2+3, 3+1, 3+2, 4+1}
P (at most 5)
= 10/36
= 5/18