Combinations
Count unordered selections of r objects chosen from n distinct objects using combinations, C(n, r). Unlimited questions, five difficulty levels, and a full worked solution every time — free.
Try one
A teacher must choose 2 students from a class of 6 to represent the class on a trip. How many different groups of 2 students are possible?
C(6, 2) = n! / (k! (n - k)!)
Answer: 15
See one solved, step by step
A teacher must choose 3 students from a class of 8 to represent the class on a trip. How many different groups of 3 students are possible?
C(8, 3) = n! / (k! (n - k)!)
📘 Worked solution
1C(8, 3) = (8 · 7 · 6) / 3!Combinations use the same descending product as permutations, then divide by 3! to remove the ordering within the group.
2= 336 / 6 = 56Compute the top (336) and bottom (6), then divide.
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