A student has a five digited id card number. If you choose a student, what is the probability of 'not' having same number on it(i.e. 22056, there's 2)?
There are 100000 such id cards. Any digit for example '0' can be placed in the number in $2^5$ ways. But of them, there are 5+1=6 such ways where '0' is only one. So, it is not acceptable. So, $2^5 -6 = 26$ . For each digit(0-9) it is 26*10 = 260. So the probability is, (260/100000)*100% = .26% Am I right?{it seems not }
Barisal HS 2009_12
Forum rules
Please don't post problems (by starting a topic) in the "X: Solved" forums. Those forums are only for showcasing the problems for the convenience of the users. You can always post the problems in the main Divisional Math Olympiad forum. Later we shall move that topic with proper formatting, and post in the resource section.
Please don't post problems (by starting a topic) in the "X: Solved" forums. Those forums are only for showcasing the problems for the convenience of the users. You can always post the problems in the main Divisional Math Olympiad forum. Later we shall move that topic with proper formatting, and post in the resource section.
-
- Posts:78
- Joined:Thu Jan 20, 2011 10:46 am
Re: Barisal HS 2009_12
just use the concept of box. let you 5 boxes and you want to fill the box with different digits
now you have 9 ways to fill the 1st box as the id card number is 5 digit number you dont use 0 on it and now you have also 9 ways to fill the 2nd box and 8 ways for 3 rd boxs so the result is 9.9.8.7.6. and you have 99999 five digit number ( i use the id numbers are five digit number if there exist this type of id number 01973 there will be slight change in result)
now you have 9 ways to fill the 1st box as the id card number is 5 digit number you dont use 0 on it and now you have also 9 ways to fill the 2nd box and 8 ways for 3 rd boxs so the result is 9.9.8.7.6. and you have 99999 five digit number ( i use the id numbers are five digit number if there exist this type of id number 01973 there will be slight change in result)
Re: Barisal HS 2009_12
শিশির ভাই, আইডি কার্ড এ তো প্রথম অঙ্ক ০ হতেও পারে??
Please Install $L^AT_EX$ fonts in your PC for better looking equations,
Learn how to write equations, and don't forget to read Forum Guide and Rules.
"When you have eliminated the impossible, whatever remains, however improbable, must be the truth." - Sherlock Holmes
Learn how to write equations, and don't forget to read Forum Guide and Rules.
"When you have eliminated the impossible, whatever remains, however improbable, must be the truth." - Sherlock Holmes
- nafistiham
- Posts:829
- Joined:Mon Oct 17, 2011 3:56 pm
- Location:24.758613,90.400161
- Contact:
Re: Barisal HS 2009_12
yes, i also think the same way.if it is, the answer will just be
\[\frac{(10-5)!}{10^6}\]
of course, Mehfuj Zahir has mentioned about it,too.
\[\frac{(10-5)!}{10^6}\]
of course, Mehfuj Zahir has mentioned about it,too.
\[\sum_{k=0}^{n-1}e^{\frac{2 \pi i k}{n}}=0\]
Using $L^AT_EX$ and following the rules of the forum are very easy but really important, too.Please co-operate.
Using $L^AT_EX$ and following the rules of the forum are very easy but really important, too.Please co-operate.
- bristy1588
- Posts:92
- Joined:Sun Jun 19, 2011 10:31 am