If all of the telephone extensions in a certain company must be even numbers, and if each of the ...
If all of the telephone extensions in a certain company must be even numbers, and if each of the extensions uses all four of the digits 1, 2, 3, and 4, what is the greatest number of four-digit extensions that the company can have?
Answer/Solution
12
Steps/Work
Since the phone number must be even, the unit's digit can be either 2 or 4.
When the unit's digit is 2 --> number of possibilities is 3! = 6
When the unit's digit is 4 --> number of possibilities is 3! = 6
Largest number of extensions = 6 + 6 =12
Answer:C
When the unit's digit is 2 --> number of possibilities is 3! = 6
When the unit's digit is 4 --> number of possibilities is 3! = 6
Largest number of extensions = 6 + 6 =12
Answer:C