Q1) How many dissimilar computer passwords are possible?

a) If each password comprises of three symbols and if first one should be a number and other 2 should be letters

b) If each password comprises of 3 symbols and if first one should be a Letter and the other 2 should be Numbers

c) Which one do you think is more secure and why?

Q2) Automobile license plate comprises of 3 letters followed by 4 digits.  How many different plates can be made?

a) If repetitions are permitted

b) If repetitions are not permitted

c) If repetitions are allowed in the letters but not in digits.