5 exercises · 5 automatically checked · Untimed
5 questions · Shuffled order · Untimed practice
Work through the questions before checking solutions. Guide question labels stay the same when you shuffle the bank. Use an exact fraction when a decimal would require rounding.
Guide question labels stay the same when the order changes. Check answers when you are ready to review.
Written responses are self-review exercises.
Saved on this browser and device; clearing browser data removes progress.
Your practice is saved on this device.
A box has 6 silver, 9 gold, and 5 black tokens. One token is selected uniformly at random. What is the probability that it is gold?
Enter an integer, decimal or fraction without units. Use up to 5 characters, or 6 including a leading minus.
Answer: 9/20
There are 20 equally likely individual tokens, 9 of them gold. The probability is 9/20. Three colors do not imply equal color probabilities.
Review worked example 5.01.
Of 30 club members, 12 pay for an event. Of 50 nonmembers, 8 pay. Given that a randomly selected person from these 80 people is a club member, what is the probability that the person pays?
Enter an integer, decimal or fraction without units. Use up to 5 characters, or 6 including a leading minus.
Answer: 2/5
Condition on the 30 members. Twelve pay, so the conditional probability is 12/30
Review worked example 5.05.
Of 60 students, 32 take art, 25 take music, and 12 take both. What is the probability that a randomly selected student takes art or music, or both?
Enter an integer, decimal or fraction without units. Use up to 5 characters, or 6 including a leading minus.
Answer: 3/4
The union count is 32 + 25 − 12
Review worked example 5.07.
A bag contains x red counters and 18 blue counters. The probability of drawing red is 2/5. What is x?
Enter an integer, decimal or fraction without units. Use up to 5 characters, or 6 including a leading minus.
Answer: 12
The probability equation is x/(x + 18)
Review worked example 5.08.
Supplier A makes 80% of parts and has a 1% defect rate. Supplier B makes 20% and has a 4% defect rate. Given that a randomly selected part is defective, what is the probability that it came from B?
Enter an integer, decimal or fraction without units. Use up to 5 characters, or 6 including a leading minus.
Answer: 1/2
The shares of all parts that are defective from A and B are 0.80(0.01)
Review worked example 5.15.
Review Probability and conditional probability