Answer to Question #68679 in Statistics and Probability for Kenny

Question

How many 3 digits numbers greater than 300 can be formed using the digits 1, 2, 3, 4, 5 if no digit can be repeated and the first digit cannot be 3?

Answer 1

We have that a number is larger than 300 and its first digit cannot be 3. Then the first digit is 4 or 5.
The number of possibilities is 2 times the number of permutations of the remaining 4 digits taken 2 at a time
2P_(4,2)=2∙4!/(4-2)!=2∙4∙3=24
Answer: 24 numbers.