MATH 141 In-Class Exercise on Probability

Names_______________________________________________________

1. A bag contains 20 balls numbered 1-20 of the following colors:

1-5 Red, 6-10 White, 11-20 Green. One ball is selected at random from the bag. Find each of the following probabilities.

a) P(Red) =_______, b) P(Even) =_______, c) P(Red and Even) =_______,

d) P(Red or Even) =_______, e) P(White and Less than 8) =_______,

f) P(White and not Red) =_______, g) P(Green or divisible by 3) =_______.

2. Using the bag from Problem 1, two balls are selected in order from the bag without replacement. Find the following probabilities:

a) P(Balls are same color) =_______, b) P(Sum is 10) =_______,

c) P(Balls are different color) =_______,

d) P(First ball is white and second ball is even) =_______.

3. A bag contains the letters from the name SOUTH DAKOTA (with all repetitions, that is, the bag contains two T’s for example). One letter is chosen at random from the bag.

a)Write out the elements of the sample space, S, for this experiment. S = _____________.

b) What is the probability of selecting a vowel? P(Vowel) =______.

c) If four letters are chosen from the bag in order without replacement, what is the probability that the letters spell the word TOAD? P(TOAD )= _________

d) Repeat c) except that the letters are chosen with replacement. P(TOAD )= _________

4. A bag contains 6 blue marbles and 4 yellow marbles. 3 marbles are drawn from the bag without replacement. Find each of the following probabilities:

P(More Blue than Yellow Marbles) = ________

P(All Yellow) = ________

P(Exactly one Blue) =________