1 Like
ABC, Reason：the number of ways to …without replacement basically means the number we choose is a product of three consecutive numbers , thus 24=2x3x4; 60=3x4x5; 120=4x5x6; etc etc. not sure how to solve this by using combinatorics. 
Edit: no A cuz the least value of n is 5 (5C3=10）
only BC
no, 6C3 is 20; 5C3 is 10. Therefore, n= 5 and 6. Then solutions are 60 (5x4x3) and 120 (6x5x4)
ahh yes! my mistake Thanks for correction 