Probability

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babybells96

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Dec 20, 2012
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I need help with this word problem, please.

A pet store has 18 green birds (5 females and 13 males) and 25 blue birds (15 females and 10 males). You randomly choose one of the birds. What is the probability that it is a male or a blue bird.

Thank you so much!
 
Last edited:
babybells96 said:
I need help with this word problem, please.

A pet store has 18 green parakeets (5 females and 13 males) and 25 blue parakeets (15 females and 10 males). You randomly choose one of the parakeets. What is the probability that it is a male or a blue parakeet?

Thank you so much!
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Okay, I'm sorry. I didn't understand. I'm new to the website.

So far, I have counted up the grand total of birds 18+25 to get 43, which I think is the total. And I think I need to find the probability of both getting a male and getting a blue parakeet. There are 23 males and 25 blue parakeets. So, I think I would do 23/34 + 25/43 and add them together to get 48/43? That doesn't sound right to me. I think I messed something up.
 
You're right, there are 43 parakeets total. 23 males, 25 blues and 10 blue males (which you have counted twice). Hence, the probability is:

\(\displaystyle P(X)=\dfrac{23+25-10}{43}=\dfrac{38}{43}\)

An alternate approach would be to observe that is it certain you will choose either a green female (event A) or not choose a green female (event B), i.e., either get a blue or a male. We may then write:

\(\displaystyle P(A)+P(B)=1\)

\(\displaystyle P(B)=1-P(A)=1-\dfrac{5}{43}=\dfrac{43-5}{43}=\dfrac{38}{43}\)
 
Glad to help, and welcome to the forum! :mrgreen:
 
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