How many different ways can 2 students be seated in a row of 7 desks , so that there is always at least one empty desk between the students
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3 ways to seat the students:
with two empty seats between
1 empty w/ one student on the left most
1 empty....right most
two students can be interchanged
3x2=6
with two empty seats between
1 empty w/ one student on the left most
1 empty....right most
two students can be interchanged
3x2=6
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nCr = n!/ (n-r)!*r!
we have n = 4 and r = 2
nCr= 4*3*2*1/ ( 4-2) ! * 2 *1
= 4*3/ 2*1 = 6
However sometimes it is easier to find out the soln. using the basic method as shown by GMAT-HELP.
we have n = 4 and r = 2
nCr= 4*3*2*1/ ( 4-2) ! * 2 *1
= 4*3/ 2*1 = 6
However sometimes it is easier to find out the soln. using the basic method as shown by GMAT-HELP.
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