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A person has the following bills: $1,$5, $10,$20, $50. How  Question banks Downloads My Bookmarks Reviews Important topics Author Message Senior Manager Joined: 30 Aug 2003 Posts: 324 Location: dallas , tx Followers: 1 Kudos [?]: 18 [0], given: 0 A person has the following bills:$1, $5,$10, $20,$50. How [#permalink]  02 Oct 2003, 08:41
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A person has the following bills: $1,$5, $10,$20, $50. How many unique sums can one form using any number of these bills only once? _________________ shubhangi Intern Joined: 29 Aug 2003 Posts: 49 Location: Detroit, MI Followers: 0 Kudos [?]: 2 [0], given: 0 Re: PS [#permalink] 02 Oct 2003, 09:10 shubhangi wrote: A person has the following bills:$1, $5,$10, $20,$50. How many unique sums can one form using any number of these bills only once?

Num of unique sums we get using 1 bill at a time = 5
Num of unique sums we get using 2 of the 5 bills at a time = C(5,2) = 10
Num of unique sums we get using 3 of the 5 bills at a time = C(5,3) = 10
Num of unique sums we get using 4 of the 5 bills at a time = C(5,4) = 5
Num of unique sums we get using 5 bills at a time = 1

So, answer = 5 + 10 + 10 + 5 + 1 = 31

Am I right?
Senior Manager
Joined: 30 Aug 2003
Posts: 324
Location: dallas , tx
Followers: 1

Kudos [?]: 18 [0], given: 0

again ..am confused
_________________

shubhangi

SVP
Joined: 03 Feb 2003
Posts: 1604
Followers: 8

Kudos [?]: 147 [0], given: 0

Agree, it is 5C1+5C2+5C3+5C4+5C5=5+10+10+5+1=31
Senior Manager
Joined: 30 Aug 2003
Posts: 324
Location: dallas , tx
Followers: 1

Kudos [?]: 18 [0], given: 0

Okay !!
that's easy to understand.. thanks
_________________

shubhangi

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