Saturday

March 28, 2015

March 28, 2015

Posted by **Sana** on Sunday, October 15, 2006 at 10:37am.

I'm not entirely sure what you question is asking, but I'll take a guess.

You have n digits and k 1's with k<n

There are n choose k ways to arrange the 1's in your number.

You now have n-k places to choose the other 9 numbers. There are two cases to consider: when the fist digit is 1 and when it isn't. If it's not 1 then there are only 8 digits you can use, since a number wouldn't have 0 in the lead position. If it is a 1 then there are 9 possible choices for each of the n-k position or 9

I see someone else posted this question too and they said leading 0's are acceptable, so you can disregard part of the previous post if you have the same quesiton as them.

There are n choose k ways to arrange the 1's and 9

n choose k * 9

**Answer this Question**

**Related Questions**

math - How many n-digit decimal sequences (using digits 0-9) are there with k 1s...

math - using digits 1-9 only once, multiply a 3 digit by a 2 digit number and ...

data management - from the digits 0,1,2,3,4,5,6,7,8,9 find the number of a) 4-...

Data management - from the digits 0,1,2,3,4,5,6,7,8,9 find the number of a) 4-...

math - Can u please help me with this..this is my sons 6th grade work and im ...

math - Posted by nicole on Monday, September 22, 2008 at 4:32pm in response to ...

math - Posted by nicole on Monday, September 22, 2008 at 4:32pm in response to ...

Math (Reiny) - Regarding my question below, when the question talks about digits...

math - A 4-digit number. The sum of its digits is 18. The last two digits are 5 ...

math - how many different sequences of 4 digits possible if the first digit must...