Combinations And Permutations

Question 1

Combination

Answer 1

Used when order in which a task is completed doesn’t matter

Question 2

Permutation

Answer 2

When the order in which a task is completed does matter

Question 3

Combination formula (basic)

Answer 3

N!
________
(N - k)!k!

N is the number of objects from which you’ll choose
K is the number of objects you will actually choose

Question 4

Handshake questions

Answer 4

Any question counting that asks us to determine the number of ways to connect any two members of a group while also meeting any restrictions that may exist

Nk
___
2

N is the number of entities and k is the number of entities n is connected to

Question 5

nCk

Answer 5

= nCn-k

Question 6

If n x and y are non negative integers such that nCx = nCy then

Answer 6

N = x+y

Question 7

If there are m ways to perform task 1 and n ways to perform task 2 and the tasks are independent then there are _____ ways to perform both tasks together

Answer 7

M x n

Question 8

Number of configurations that can be made when restricting two people being in a group together

Answer 8

Number of configurations where both people are both in - number of configurations where neither are in

Question 9

Basic permutation

Answer 9

n!
____
(n-k)!

Question 10

In permutation problems how do you handle identical items

Answer 10

Only should be counted once

Question 11

Permutations for indistinguishable items

Answer 11

P = N!
____________
R1! X R2!…

Where R represents the number of each indistinguishable objects

Ie AAB
3!
___
2!

Question 12

If a 2 dimensional pathway involves one or more checkpoints, we can determine the total number of pathways from starting point to destination by:

Answer 12

1.) identify every checkpoint (points travelers MUST pass through
2.) determine the number of ways to travel between each pair of successive checkpoints
3.) calculate the product of all results from 2