Practice Combination in Math

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

A combination is an unordered selection of objects โ€” the number of ways to choose rr items from nn distinct items is C(n,r)=n!r!(nโˆ’r)!C(n,r) = \frac{n!}{r!(n-r)!}.

How many ways to choose a group? {A,B,C}={C,B,A}\{A, B, C\} = \{C, B, A\}.

Showing a random 20 of 50 problems.

Example 1

easy
Compute C(8,1)C(8,1).

Example 2

medium
From 10 marbles (4 red, 6 blue), how many ways to pick 3 marbles with exactly 1 red?

Example 3

easy
How many ways to choose a 4-person subcommittee from a group of 6?

Example 4

medium
A pizza shop offers 10 toppings. How many distinct pizzas use 4 different toppings?

Example 5

medium
From 8 people, choose 4 such that two specific people, Bob and Carol, are NOT both included.

Example 6

medium
Solve for nn: C(n,2)=21C(n,2)=21.

Example 7

easy
A jar holds 5 different fruits. How many distinct fruit salads of 3 different fruits can be made? (Order does not matter inside a salad.)

Example 8

easy
Compute C(6,2)C(6,2).

Example 9

easy
A committee of 33 is to be chosen from 88 people. How many different committees are possible?

Example 10

medium
How many ways to split 6 distinct items into a chosen group of 4 and leave 2 behind?

Example 11

medium
How many ways can you choose 44 books from a shelf of 1010 books?

Example 12

easy
Compute C(5,2)C(5,2).

Example 13

easy
Fill in the blank: C(n,n)=โ€พC(n, n) = \underline{\quad}.

Example 14

medium
How many diagonals does a convex hexagon (6 vertices) have?

Example 15

medium
How many 5-card poker hands are there from a 52-card deck?

Example 16

easy
Use symmetry to find C(10,8)C(10,8).

Example 17

easy
How many ways to choose 2 toppings from 5 (order does not matter)?

Example 18

hard
A 4-card hand is drawn from a 52-card deck. What is the probability the hand contains all 4 aces?

Example 19

easy
How many ways can a teacher choose 2 students from a class of 9 to be hall monitors?

Example 20

medium
A committee of 3 is chosen from 7 people. How many committees are possible?