To log on to a certain computer account, the user must type in a 4-letter password. In such a password, no letter may be repeated, and only the lower case of a letter may be used. How many such 4-letter passwords are possible

 358800

Step-by-step explanation:

To create a four-letter password such that no letter are repeated and only lower cases are used;

For the first letter, we can choose any letter from A to Z = 26

We can choose any letter from A to Z except for the first letter for the second letter. = 25

We can choose any letter from A to Z except for the first & second letter for the third letter. = 24

We can choose any letter from A to Z except for the first, second & third letters for the fourth letter. = 23

SO;

No of ways in which 4-letter passwords are possible = 26 × 25 × 24 × 23

No of ways in which 4-letter passwords are possible =  358800

The students went on vacation for average 40 days.

The high school students went for more days than college students.

Step-by-step explanation:

The data shows number of students who went for vacation. The data class frequency shows that students who are in high school went for more days in vacation than college students. The students went for average of 40 days on vacation.