# StudySquare

# SQA National 5 Maths Independent outcomes

This page covers the following topics:

If the probability of a 1st event happening has no impact on the probability of a 2nd event happening then the two events are independent.

When finding the probabilities for independent outcomes, we can use the and rule. If event 1 happens AND event 2 also happens, we multiply the probabilities.

We can use the OR rule when calculating the probability of either of 2 different events occurring. If asked to find the probability of event A or event B happening, we must add the probabilities.

# 1

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Stewart is getting the bus to his dentist appointment. The bus service is unreliable and the probability that his bus is running late is 5/8. He does not want to miss his appointment so calculates the probability his appointment will be late based on past visits. He works out the probability that his appointment is late is 4/9. What is the probability that his bus is late and his appointment is not late?

# 2

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A man in a betting shop has placed bets on 4 independent events and he wants to know the probability that all events happen. Using his betting sheet, work out the probability that he wins all the bets.

# 3

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Jeff and Andy have gone bowling. The probability that Jeff gets a strike is 1/8 and the probability that Andy gets a strike is 2/5. The probability that Jeff misses all the pins is 1/10 and the probability that Andy misses all the pins is also 1/10. Create a table to show the following probabilities: Jeff misses and Andy gets a strike, they both get a strike, they both hit the pins but do not get a strike.

# 4

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The probabilities that 3 independent events occurs are: 0.3 (event 1), 0.4 (event 2) and 0.65 (event 3). What is the probability that events 1 and 2 happen and event 3 does not? Give your answer as a decimal.

# 5

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Two basketball teams play matches. The probability of team A winning is 0.7 and the probability of them losing is 0.25. The probability of team B winning is 0.3 and the probability of them losing is 0.35. What is the probability of both teams drawing?

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