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Mathematics 21 Online
OpenStudy (mathmath333):

A teacher has to distribute 15 pens among 5 of his students such that student A gets at least 3 and at most 6 pens.In how many ways can this be done ?

OpenStudy (mathmath333):

\(\large \color{black}{\begin{align} & \normalsize \text{A teacher has to distribute 15 pens among 5 of his students such}\hspace{.33em}\\~\\ & \normalsize \text{that student A gets at least 3 and at most 6 pens.In how many }\hspace{.33em}\\~\\ & \normalsize \text{ ways can this be done ?}\hspace{.33em}\\~\\ & a.)\ 495 \hspace{.33em}\\~\\ & b.)\ 77 \hspace{.33em}\\~\\ & c.)\ 417 \hspace{.33em}\\~\\ & d.)\ 435 \hspace{.33em}\\~\\ \end{align}}\)

OpenStudy (mathmath333):

only student A gets atleast 3 to 6 pens necessarily

OpenStudy (dan815):

lets do 4 cases then Student A 3 4 5 6

OpenStudy (dan815):

when student A gets 3 pens we have 12 pens to distribute among 4 students

OpenStudy (mathmath333):

12C4=495

OpenStudy (dan815):

u cant just do that

OpenStudy (dan815):

why are you doing 12 choose 4

OpenStudy (mathmath333):

cuz i left with 4 students and 12 pens

OpenStudy (dan815):

wait umm from your previous questions, when they ask questions like this does that mean the pens are distinguishable or not?

OpenStudy (mathmath333):

i think pens are similar/identical

OpenStudy (dan815):

okay phew that makes it a lot simpler

OpenStudy (dan815):

so we have 12 pens and 4 students think about it like stars and bars question

OpenStudy (mathmath333):

15C3

OpenStudy (dan815):

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