1) If a die is rolled once, determine the probability of rolling a 4: Rolling a 4 is an event with 1 favorable outcome (a roll of 4) and the total number of possible outcomes is 6 (a roll of 1, 2, 3, 4, 5, or 6). Thus, the probability of rolling a 4 is ¹/₆.
If a die is rolled once, determine the probability of rolling at least a 4: Rolling at least 4 is an event with 3 favorable outcomes (a roll of 4, 5, or 6) and the total number of possible outcomes is again 6. Thus, the probability of rolling at least a 4 is ³/₆ = ¹/₂.
Here are two more examples:
If a coin is flipped twice, determine the probability that it will land heads both times:
Favorable outcomes: 1 -- HH
Possible outcomes: 4 -- HH, HT, TH, TT
Thus, the probability that the coin will land heads both times is ¹/₄.
If Dan grabs one sock from a drawer containing 3 white socks, 4 blue socks, and 5 yellow socks, what is the probability that he will grab a white sock?
Favorable outcomes: 3 (3 white socks)
Possible outcomes: 12 (3 white socks + 4 blue socks + 5 yellow socks)
Thus, the probability that Dan will grab a white sock is ³/₁₂ = ¹/₄.
