Pearson Geometry Common Core, 2011
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Pearson Geometry Common Core, 2011 View details
4. Compound Probability
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Exercise 19 Page 848

Use the formula for the probability of overlapping events.

5/8

Practice makes perfect
We select a card at random from a set that contains four suits, each of which consists of cards numbered from 1 to 10.
Selecting a card at random
We are asked to find the probability that we select a red card or a card greater than 5. Note that we can choose a card that is both red and greater than 5. Since the events have an outcome in common, they are overlapping events. Let's recall the formula for P( Aor B) when A and B are overlapping events. P( Aor B)=P( A)+ P( B)-P( Aand B)

In order to find the desired probability, we will find the individual probabilities and the probability that we select a card that is both red and greater than 5. Let's start by calculating the probability of choosing a red card.

We select a red card - possible outcomes

Out of 40 cards, there are 10 red cards. P( red card)= 10/40=1/4 Next, we will calculate the probability of choosing a card greater than 5.

We select a card greater than 5 - possible outcomes

Out of 40 cards, there are 20 cards greater than 5. P( card greater than5)= 20/40=1/2 Now we will calculate the probability of both choosing a red card and choosing a card greater than 5.

We select a red card greater than 5 - possible outcomes
Out of 40 cards, there are 5 red cards greater than 5. P( red cardand card greater than5) = 5/40 = 1/8 Finally, we can find the desired probability.
P(red card or card greater than5)
P(red card)+ P(card greater than5)-P(red card and card greater than5)
1/4+ 1/2- 1/8
â–Ľ
Simplify
2/8+1/2-1/8
2/8+4/8-1/8
5/8
Therefore, the probability P(red card or card greater than 5) is equal to 58.