Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

There's a raffle:

  • 754 total entries in the raffle
  • 130 will get selected

What's the odds that I will get selected?

2nd Question:

Now, what if I have 4 of the 754 entries? What are my odds then?

Can you walk me through the math on this?

share|improve this question
1  
What have you tried? –  Cameron Buie Sep 24 '13 at 15:42
    
Odds ... and my guess for the first part was 130/754. I have no clue how to solve the 2nd part. –  Martin Sep 24 '13 at 15:43

2 Answers 2

up vote 2 down vote accepted

Hint: if you have multiple tickets, calculate the chance that you do not win and subtract from $1$. What is the chance that your first ticket loses? Given that it does, what is the chance that the next one loses-how many numbers are left?

Added: to get the chance that you have two winners out of four, you have {6 \choose 2} ways to choose the winners, so the chance is ${6 \choose 2}\cdot \frac {130}{754}\cdot \frac {129}{753} \cdot \frac {624}{752} \cdot \frac {623}{751}$. The others are similar.

share|improve this answer

Hints: How many different ways are there to choose $130$ of $754$ tickets?

If you have just one entry, then in how many ways can one of the chosen $130$ entries be yours and $9$ of them belong to other people?

If you have $4$ entries, then in how many ways can all $130$ chosen entries belong to someone else? How many ways, then, can at least one of your entries be chosen?

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.