Dinner party/Dessert Probability Question

[robinphilip01]

Hi Tommy,
The question:
"John invites 12 friends to a dinner party, half of whom are men. Exactly one man and one women are bringing desserts. If on person form this group is selected at random, what is the probability that it is a women or a man who is not bringing a dessert ? "


Here, in the answer, (11/12)
numerator- 11 as the sum of 5(men) and 6(women)
Explnation of answer sayes:
"As six women are invited and 5 men who are not bringing a dessert are invited "
Is this is 5 women and 5 men who are not bringing a dessert
as the question states exactly one man and one women are bringing the dessert?

[kucz.adam]

Hi robinphilip01,

This question is worded poorly. Read the problem as

What is the probability of selecting a women

OR

What is the probability of selecting a man who is not bringing a dessert?

SOLUTION: Because these two events are mutually exclusive (it is not possible to select a woman who is also a man not bringing a dessert!) and you are calculating the probability of one event OR the other, add the probabilities up.

p(W) + P(M not dessert) = 1/2 + 5/12 = 6/12 + 5/12 =11/12

[tommywallach]

Hey All,

Agreed the wording is confusing. Also, this question was already brought up on the board. Always do a quick search before posting, and try to describe the question in the subject (I've changed this one to reflect that).

-t