How many two-digit numbers can be formed by using the numerals in the set {1,4,6,8,9} if repetition is not allowed?
A) 20
B) 118
C) 2
D) 22
E) 10

Question

How many two-digit numbers can be formed by using the numerals in the set {1,4,6,8,9} if repetition is not allowed? ​
A) 20
B) 118
C) 2
D) 22
E) 10

Quizplus · Accepted Answer

For a two-digit number, there are 5 choices for the first digit (since it can be any of the numbers in the set) and 4 choices for the second digit (since repetition is not allowed and one number has already been used for the first digit). Therefore, the total number of two-digit numbers that can be formed is 5 * 4 = 20.

How Many Two-Digit Numbers Can Be Formed by Using the Numerals