If all of the phone extensions in a certain organisation must be even numbers, and if each of the extensions uses all four of the digits 1, 2, 3, and 6, what is the greatest number of four-digit extensions that the organisation can have?
A. 4
B. 6
C. 12
D. 16
E. 24

• The four digits available are 1,2,3 and 6
  as the extensions can only be even numbers, the last digit has to be either 2 or 6
  If it is 2...it leaves 1,3 and 6 for the first three digits...these can be arranged in 3! ways
  If the last digit is 6...it leaves 1,2 and 3 for the first three digits...these can be arranged in 3! ways
  
  Thus answer is 2*3! = 12
• 5 years agoHelpfull: Yes(1) No(0)
• the answer is 4
• 5 years agoHelpfull: Yes(0) No(0)