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a teacher is grouping 20 students in to groups containg 4 students. There are 12 americans 5 russains and 3 chinese. How many way are possible of choosing the first group such that a) at least one person from each country is there b) not all students belong to one country

usha rao , 12 Years ago
Grade
anser 2 Answers
vijay k

Last Activity: 12 Years ago

a)12c2.5c1.3c1+12c1.5c2.3c1+12c1.5c1.3c2

b) 1-12c2.5c1.3c1+12c1.5c2.3c1+12c1.5c1.3c2

usha rao

Last Activity: 12 Years ago

Thanks

for a) why can we not use 12C1 X 5C1 X 3C1 X 17C1

b) not clear..guess it is 20C4 - (12C4+5C4)

 

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