Probability of compound events worksheet for Geometry
In Geometry probability follows straight on from counting and sample spaces. For two draws from a bag, decide whether the events are independent, as when a counter is replaced, or dependent, as when it is not, and that decides which fractions to multiply. Other questions use the addition rule for or, combinations for tickets drawn at once, and the complement for at least one.
Also taught in Algebra 2, Precalculus and Statistics, each at its own level and with its own examples.
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Sigma Prep · sigmaprep.io/worksheets Name Probability of Events Date Period Find each probability.
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Sigma Prep · sigmaprep.io/worksheets Name Probability of EventsAnswer keyVersion 3 Date Period Find each probability.
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How to do these
A bag has 5 red and 3 blue counters. Two are drawn without replacement. Find P(both red).
- First draw: 5 of the 8 counters are red, so 5/8.
- One red is gone, so 4 of the 7 left are red: 4/7.
- Multiply: 5/8 × 4/7 = 20/56.
The answer is .
Where students go wrong
Keeping the same fraction on the second draw without replacement. After one red counter is taken, 7 counters are left and 4 are red, so the second factor is 4/7, not 5/8.
Also called independent events, dependent events or compound probability.
What you can put on this worksheet
- Independent events: both the same
- A spinner has 9 equal sections: 4 red and 5 blue. It is spun twice. Find the probability that it lands on red both times. →
- Independent events: one of each
- A spinner has 9 equal sections: 4 red and 5 blue. It is spun twice. Find the probability that it lands on red once and blue once. →
- Dependent events: both the same
- A class has 4 girls and 5 boys. To pick who hands out papers, the teacher draws two names from a hat, one after the other. Find the probability that both are girls. →
- Dependent events: one of each
- A class has 4 girls and 5 boys. To pick who hands out papers, the teacher draws two names from a hat, one after the other. Find the probability that the two are one of the girls and one of the boys, in either order. →
- One event or the other
- A 6-sided die is rolled. Find P(greater than 3 or less than 3). →
- Probability with combinations
- A box has 3 winning tickets out of 10. Two are drawn at once. Find P(neither is a winner). →
- Experimental probability
- A spinner was spun times and landed on red on of the spins. Find the experimental probability of landing on red. →
- At least one, by the complement
- A die is rolled 3 times. Find P(at least one 5). →
- Two different experiments: a coin and a die, a die twice
- A spinner with 5 equal sections numbered 1 to 5 is spun twice. Find P(a 5, then an even number). →
- Three picks in a set order
- A drawer has 4 black, 2 gray and 3 white socks. Three are taken at random, one after another, without putting any back. Find P(black, then black, then black). →
- Drawing from two groups: exactly so many
- A standard 52-card deck has 26 red cards and 26 black cards. Three cards are dealt at random. Find exactly 3 red. →
- Coins, dice and guessing: exactly, at least, at most
- A student guesses on every question of a 4-question true-false quiz. Find P(at most 1 right answer). →