A bag holds 2 red, 4 blue and 3 green balls. You draw one at random. What is the probability P that it is blue?
Probability worksheet with answers
1.Easy
2 / 4 / 3
P =
2.Easy
The table gives the probability distribution of X, but one probability is missing. Find P(X = 3).
x: 0, 1, 2, 3, 4p(x): 0.3, 0.15, 0.25, ?, 0.05
P(X = 3) =
3.Medium
A bag holds 3 red and 5 blue balls. You draw two balls without putting the first one back. What is the probability P that both are red?
3 / 5
P =
4.Medium
A fair die is rolled 8 times. What is the probability P of getting at least one six?
n = 8
P =
5.Hard
A test has 5 multiple-choice questions. A student who guesses gets each one right with probability 0.4, independently. What is the probability P of exactly 2 correct answers?
n = 5p = 0.4k = 2
P =
6.Hard
A game costs €3 to play. You win €6 with probability 0.3 and €30 with probability 0.02; otherwise you win nothing. The stake is not returned. Find the expected net gain E(G) per game.
stake = €3€6: p = 0.3€30: p = 0.02
E(G) = €
Answer key
- 1. P = 0.4444
- 2. P(X = 3) = 0.25
- 3. P = 0.1071
- 4. P = 0.7674
- 5. P = 0.3456
- 6. E(G) = −0.6 €
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