. A new programming language requires variable names to start with a letter (upper or lowercase), which can be followed by letters, numbers, or underscores. For example, a1_B_3 is a valid name. If every variable name has to be at least 3 characters but fewer than 7, how many variable names are possible?

Explanation:

Total letters available on the keyboard = 26

Doubling this amount to account for both upper and lower case letters.

Therefore, Total characters (Upper + Lower Case) = 52 characters

Total numbers on keyboard (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) = 10 characters

Underscore = 1 character

Thus, Total allowed characters = 52 + 10 + 1 = 63

This is a problem of the permutation as order of the characters results in a different name.

Our file name should be of atleast 3 and smaller than 7 (i.e. 6) characters

Therefore, total possible permutations can be obtained by subtraction permutation of 2 characters from the permutations of 6 characters.

volleyball players can not touch the net while the ball is in play

laticia draws the diagram below to show earth’s magnetic field.

answer

the arrows to the right of earth should point up.