Posted by Maria on Monday, February 22, 2010 at 2:50am.
If 3 people are asked what day of the week they were born, find the probability that
i) 2 or 3 are the same.
ii) only 2 people are the same.
 is this 1/7 x 1/7 ??
If 4 people are asked what day of the week they were born, what is the probability that 2 or more people were born on the same day.
 How do I show this??
Using this idea, work out how many people need to be asked for their birthdate so that at least two people sharing their birthdate will have a chance of 1/2.
Thank you

Math  PsyDAG, Monday, February 22, 2010 at 6:24am
i) It is the proportion below for 2 the same, plus 1/7*1/7*1/7 for 3 the same. (Eitheror probabilities are determined by adding the separate probabilities.)
ii) It is 1/7*1/7*6/7, because the third person has a different day of the week.
iii) Work the same as i) above, for 2, 3 or 4 sharing the same day.
The only way I know to find out is to expand iii) above to larger numbers until it equals 1/2.
I hope this helps.

Math (Oops)  PsyDAG, Monday, February 22, 2010 at 6:36am
Sorry, I was distracted by your attempt to answer ii). Your concern is for matching the first throw, whatever it is.
i) It is the proportion below for 2 the same, plus 1/7*1/7 for 3 the same. (Eitheror probabilities are determined by adding the separate probabilities.)
ii) The first throw can be any number, so your concern is with matching that number, so ii) = 1/7*6/7.
iii) Work the same as i) above, for 2, 3 or 4 sharing the same day.
The only way I know to find out is to expand iii) above to larger numbers until it equals 1/2.
Answer This Question
Related Questions
 Maths   In a normal pack of cards, write down the odds against picking each ...
 Math  What is the probability that at least 2 people in a random group of 4 ...
 math  Bo asked Luke to guess what month and day of the week he was born. If all...
 Probability  If three people are randomly selected, find the probability that ...
 math  the smallest number of people in a room where the probability of two of ...
 World Geography  Which statement describes negative population growth? A) Fewer...
 math  Six people are asked to pick a number from 1 to 20. What is the ...
 math  what is the smallest number of people that must be gathered together to ...
 math  How many people do you need in a room in order to guarantee that there is...
 12 math  there are 8 opposite sex married couples at a party. two people are ...
More Related Questions