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Apply probability across unfamiliar problems

Apply probability across unfamiliar problems: original cases with explanations after your first response.

Paper packet. Every task here also exists on screen, where it is checked automatically; answers written on paper are not assessed by Nydus. When you are back at a device, enter your answers there.

1. What you will learn

Define the sample space before assigning probabilities. Decide whether selection replaces an item and whether the second event depends on the first.

2. Practice

A fair six-sided die is rolled. What is the probability of a result greater than 4? Enter a fraction.

Answer:

3. Practice

A box contains 5 red and 3 blue balls. Two are drawn without replacement. What is the probability both are blue? Enter a fraction.

Answer:

4. Practice

Independent events A and B have probabilities .4 and .3. What is the probability that at least one occurs?

Answer:

5. Practice

Of 80 people, 45 speak language A, 30 speak B and 12 speak both. How many speak neither?

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6. Practice

Among 100 people, 50 use A, 40 use B, 30 use C; pairwise overlaps AB, AC and BC are 20,15 and 10, each including the 5 who use all three. How many use at least one?

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7. Practice

A medical-study table has 24 participants with both condition A and exposure B, and 60 participants with exposure B overall. What fraction of exposed participants have A?

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8. Practice

Events A and B are mutually exclusive, with probabilities .2 and .5. What is P(A or B)?

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9. Practice

For events A and B, P(A)=.7, P(B)=.6 and P(A and B)=.4. What is P(neither)?

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10. Practice

A bag holds cards numbered 1 through 12. Given that a uniformly drawn card is even, what is the probability it is divisible by 3? Enter a fraction.

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11. Practice

A game pays 10 with probability .2 and 0 otherwise. Its entry fee is 3. What is the expected net payoff?

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12. Practice

A device works with probability .9. Two devices work independently. What is the probability exactly one works?

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13. Practice

Factory A makes 60 percent of a shipment with a 2 percent defect rate; factory B makes the rest with a 5 percent defect rate. Given that a randomly chosen item is defective, what is the probability it came from B? Enter a fraction.

Answer:

14. What you can do now

Check with a complement or an explicit count of outcomes, ensuring that overlapping events are not added twice.