A bag holds 8 red, 5 blue and 2 green balls. You draw one at random. What is the probability P that it is blue?
Probability worksheet with answers
1.Easy
8 / 5 / 2
P =
2.Easy
Two fair dice are rolled. What is the probability P that the sum is exactly 8?
2 dice= 8
P =
3.Medium
For the distribution shown, find the variance Var(X) of X.
x: 0, 1, 2, 3, 4p(x): 0.15, 0.25, 0.35, 0.1, 0.15
Var(X) =
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 game costs €2 to play. You win €8 with probability 0.25 and €40 with probability 0.02; otherwise you win nothing. The stake is not returned. Find the expected net gain E(G) per game.
stake = €2€8: p = 0.25€40: p = 0.02
E(G) = €
6.Hard
A test has 11 multiple-choice questions. A student who guesses gets each one right with probability 0.6, independently. What is the probability P of exactly 2 correct answers?
n = 11p = 0.6k = 2
P =
Answer key
- 1. P = 0.3333
- 2. P = 0.1389
- 3. Var(X) = 1.527
- 4. P = 0.7674
- 5. E(G) = 0.8 €
- 6. P = 0.00519
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