+0  
 
0
271
2
avatar

Hello our question is,

 

If a group of 80 schoolgirls consists of 54 dancers and 35 singers, each member of the group is either a dancer or singer or both. The probability that a randomly selected student is a singer given that she is a dancer is?

 

Thanks

Guest Feb 16, 2015

Best Answer 

 #2
avatar+81055 
+5

Let A be the the probability that she is a dancer = 54/80  = 27/40

Let B be the probability that she is a singer = 35/80 = 7/16

And the probability of A and B = (A ∩ B) = 9/80

So the probability of B, given A, is just

P(B l A ) = P ( A ∩ B) / P(A) = (9/80) /(27/40) = (9/80)(40/27)  =(1/2)(1/3) = 1/6

This makes sense....there are 54 dancers and 9 of them sing, as well. So...9/54 = 1/6

 

CPhill  Feb 16, 2015
Sort: 

2+0 Answers

 #1
avatar+91475 
+5

80-54-35=-9

so

80 children,    45 dance only,   26 sing only,    9 dance and sing

 

P(S|D)= 9/54 = 1/6

Melody  Feb 16, 2015
 #2
avatar+81055 
+5
Best Answer

Let A be the the probability that she is a dancer = 54/80  = 27/40

Let B be the probability that she is a singer = 35/80 = 7/16

And the probability of A and B = (A ∩ B) = 9/80

So the probability of B, given A, is just

P(B l A ) = P ( A ∩ B) / P(A) = (9/80) /(27/40) = (9/80)(40/27)  =(1/2)(1/3) = 1/6

This makes sense....there are 54 dancers and 9 of them sing, as well. So...9/54 = 1/6

 

CPhill  Feb 16, 2015

14 Online Users

avatar
We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.  See details