1. ## Need help

hey guys, I found this forum using google. and I really hope you guys can help me.
This is the question:

Every box of a smartphone has a coupon with a number inside. the number can be: 1,2,3,4,5. If someone get all the coupons with all the numbers, he win a free phone.

the first question is: "what is the probability of a person who bought 5 phones, NOT to win a free phone". and the answer is:0.9616. - this part wasn't the problem.

The following question, is the one I cannot solve:
"What is the probability of a person who bought 8 phones, to win a free phone"

the problem I have is that now he is buying 8 phones, and I'm not sure what I need to do...

Any help would be greatly appreciated.

2. ## Re: Need help

If you worked out the probability of no win with 5 phones, you should be able to work out the probability of no win with 8 phones easily.
Once you know that you can make use of the idea that the sum of all probabilities equals 1 to work out the probability of winning with 8 phones.

3. ## Re: Need help

in order to answer the first question I found out what is the probability to win, than did 1-probability .

I've been siting on this for about 6 hours now, still no idea what to do

4. ## Re: Need help

Six hours, seriously. I looked this up on the web in about 5 minutes. See the following link for a comparable problem. You might want to double check my numbers. Good luck.

1- [ (4/5)^8 - (3/5)^8 - (2/5)^8 - (1/5)^8 ]

http://math.stackexchange.com/questi...number-of?lq=1

5. ## Re: Need help

Originally Posted by hlsmith
Six hours, seriously. I looked this up on the web in about 5 minutes. See the following link for a comparable problem. You might want to double check my numbers. Good luck.

1- [ (4/5)^8 - (3/5)^8 - (2/5)^8 - (1/5)^8 ]

http://math.stackexchange.com/questi...number-of?lq=1
thank you!!!

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