hi, so i am reviewing for a final in probability and i like totally forgot how to figure out probs like these! please help
in a bag are 5 red, 9 blue, and 6 white marbles. 2 are selected at random. what's the probability for 1 red and 1 blue?
suppose you select two letters from the word algebra. what is the probability of selecting 2 letters and having the following occur? 1 vowel and 1 consonant?
Thanks! just one answer will suffice!
in a bag are 5 red, 9 blue, and 6 white marbles. 2 are selected at random. what's the probability for 1 red and 1 blue?
suppose you select two letters from the word algebra. what is the probability of selecting 2 letters and having the following occur? 1 vowel and 1 consonant?
Thanks! just one answer will suffice!
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For both problems, you need to add up the total items.
In the case of the Marbles, that's 20. For the letters in "algebra", that's 7.
Then do the following:
1st: Calculate the probability of 1 of the events. For example, choosing 1 Red marble is 5/20 or 25%.
2nd: Calculate the probability of the 2nd event, BUT be careful - the denominator will now be reduced by 1 because the 1st event has already happened. For example, after choosing 1 Red Marble, there are now only 19 left, so the probability of choosing a Blue marble is NOT 9/20, it's 9/19.
3rd: Multiply the 2 probabilities together.
Here's how it works out for the Marbles.
1 Red Marble: 25% chance
1 Blue Marble: 9/19 = 47.37% chance.
1 Red & 1 Blue = 25% * 47.37% = 11.84%
Now use the same concept for the 2nd problem. The math works no matter which event you choose as happening first - just remember to reduce the denominator from 20 to 19 (or from 7 to 6 in the 2nd problem).
In the case of the Marbles, that's 20. For the letters in "algebra", that's 7.
Then do the following:
1st: Calculate the probability of 1 of the events. For example, choosing 1 Red marble is 5/20 or 25%.
2nd: Calculate the probability of the 2nd event, BUT be careful - the denominator will now be reduced by 1 because the 1st event has already happened. For example, after choosing 1 Red Marble, there are now only 19 left, so the probability of choosing a Blue marble is NOT 9/20, it's 9/19.
3rd: Multiply the 2 probabilities together.
Here's how it works out for the Marbles.
1 Red Marble: 25% chance
1 Blue Marble: 9/19 = 47.37% chance.
1 Red & 1 Blue = 25% * 47.37% = 11.84%
Now use the same concept for the 2nd problem. The math works no matter which event you choose as happening first - just remember to reduce the denominator from 20 to 19 (or from 7 to 6 in the 2nd problem).
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Great - glad to have helped!
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