Problema Solution
You can only fir 7 out of 20 children in your van for a trip to the zoo, how many different groups of 7 can you drive?
Answer provided by our tutors
C(20, 7) = 20!/(7!(20-7)!) = 20!/(7!13!) = (14*15*16*17*18*19*20)/(2*3*4*5*6*7) = 77520 different groups of 7.