combinatorics

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Mahfuz Sobhan
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combinatorics

Unread post by Mahfuz Sobhan » Sun Aug 02, 2015 6:06 pm

There are 9 committees with each committee having 20 members and any two committee have 5 members in common then find the minimum number of distinct members in this group.....

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Tasnood
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Re: combinatorics

Unread post by Tasnood » Fri Feb 09, 2018 10:38 pm

Let $5$ members be common for all $9$ committees [Let they be called VIP]
So, the number of non-VIP members of each committee is=$20-5=15$ and, in total=$15 \times 9=135$
Adding the VIP, the number of total members=$135+5=140$

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M. M. Fahad Joy
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Re: combinatorics

Unread post by M. M. Fahad Joy » Sat Feb 17, 2018 9:25 pm

Tasnood wrote:
Fri Feb 09, 2018 10:38 pm
Let $5$ members be common for all $9$ committees [Let they be called VIP]
So, the number of non-VIP members of each committee is=$20-5=15$ and, in total=$15 \times 9=135$
Adding the VIP, the number of total members=$135+5=140$

Sorry, don't understand. Would you please make understand me?
You cannot cross the sea merely by standing and staring at the water.

samiul_samin
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Re: combinatorics

Unread post by samiul_samin » Sat Feb 17, 2018 10:45 pm

Hint
use Addition Principle,Multiplication Principle

samiul_samin
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Re: combinatorics

Unread post by samiul_samin » Sat Feb 17, 2018 10:47 pm


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M. M. Fahad Joy
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Re: combinatorics

Unread post by M. M. Fahad Joy » Sun Feb 18, 2018 8:18 am

Thanks a lot.
You cannot cross the sea merely by standing and staring at the water.

samiul_samin
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Re: combinatorics

Unread post by samiul_samin » Sun Feb 18, 2018 9:48 am

M. M. Fahad Joy wrote:
Sat Feb 17, 2018 9:25 pm
Tasnood wrote:
Fri Feb 09, 2018 10:38 pm
Let $5$ members be common for all $9$ committees [Let they be called VIP]
So, the number of non-VIP members of each committee is=$20-5=15$ and, in total=$15 \times 9=135$
Adding the VIP, the number of total members=$135+5=140$

Sorry, don't understand. Would you please make understand me?
You can get many information about combinatorics here

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M. M. Fahad Joy
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Re: combinatorics

Unread post by M. M. Fahad Joy » Sun Feb 18, 2018 10:00 am

Wow... It is like a whole course in Bangla. The administrators should active these forums all the time.
You cannot cross the sea merely by standing and staring at the water.

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M. M. Fahad Joy
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Re: combinatorics

Unread post by M. M. Fahad Joy » Sun Feb 18, 2018 10:09 am

Here 5 members are common in two committee, not nine.
But why?
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samiul_samin
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Re: combinatorics

Unread post by samiul_samin » Sun Feb 18, 2018 10:20 am

You get wrong.It is two committee it is any two committee.

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