Question

Find the following probabilities:

A. The probability of drawing a red card or an ace when you pick a single card from a standard deck.

B. 70% of teens have cell phones. You select three random teens. What is the probability that exactly two of them have cell phones?

C. The probability of rolling a fair die and getting a 5 or greater.

D. There are 10 red jelly beans, 8 blue jelly beans, and 12 white jelly beans in a jar, and you pick out three jelly beans, one at a time, without replacement. What is the probability that they are all blue?

D. You flip a fair coin three times. What is the probability that you get exactly two tails?

Answer 1

a) There are a total of 26 red cards in a deck of cards and 2 non red ace cards.

Therefore total probability here is computed as:

Therefore 0.5385 is the required probability here.

b) Probability that exactly two of them cell phones is computed as:

c) The probability of getting a 5 or greater is computed as:

P(X = 5) + P(X = 6)

= 2/6

= 0.3333

Therefore 1/3 = 0.3333 is the required probability here.

d) Probability that all 3 jelly beans taken out are blue is computed here as:

= Number of ways to take out 3 out of 8 blue beans / Total number of ways to drawn out 3 beans out of 30 beans

Therefore 0.0138 is the required probability here.

d) Exactly two tails could be obtained in 3 ways: TTH, THT, HTT

Therefore the required probability here is: = 3*0.5³ = 0.375

Therefore 0.375 is the required probability here