Question 1003511
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From 5 statistician and 6 economists a committee consisting of 3 statistician and 2 economists is to be formed. 

How many different committees can be formed if two particular statisticians must be in the committee. 
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You have the choice of  1  statistician of  3  (two other particular statisticians are not the subject of choice) 

and  {{{C[6]^2}}} = {{{(6*5)/2}}} = 3*5 = 15  options to select  2  economists of  6.


In total,  you have  3*15 = 45  options.