SOLUTION:
GOAL: You are being asked to find the probability of getting a sum less
than 4.STRATEGY: A sum less than 4 means a sum of 2 or 3. They are (1, 1), (1, 2),
and (2, 1). Hence there are 3 ways to get a sum less than 4, and there are 36
outcomes in the sample space.IMPLEMENTATION:P(sum less than 4)¼3
36
¼
1
12
.
EVALUATION: Use the sample space to verify the answer.Probability problems also use ordinary playing cards. In a deck of cards,
there are 52 cards consisting of four suits: hearts and diamonds, which are
red, and spades and clubs, which are black. In addition, there are 13 cards in
each suit, ace through ten and a jack, a queen, and a king (called face cards).EXAMPLE:A card is drawn from a deck. Find the probability that it is
a seven.SOLUTION:GOAL: You are being asked to find the probability that the selected card is
a seven.STRATEGY: There are 52 outcomes in the sample space and 4 sevens.IMPLEMENTATION:P(seven)¼4
52
¼
1
13
.
EVALUATION: Use the sample space to verify the answer.EXAMPLE:A card is selected from a deck; find the probability that it is
a spade.SOLUTION:GOAL: You are being asked to find the probability of selecting a spade.STRATEGY: There are 13 spades in a deck of 52 cards.270 LESSON 22 Word Problems in Probability