Question

Aston University creates a 10 digit student number as the University enrolls each student. The first two characters must be a digit 1 through 9. The next seven characters can be anything and the last digit just can’t be the same as the ninth character (i.e. the previous digit). How many student numbers are possible?

Answer 1

The number of student numbers that are possible = 729,000,000 student numbers

Explanation:

The number of possible numbers that can take the place of the first two digits = 9 possible numbers each

The number of possible numbers that can take the place of the 3rd to the 9th digits = 10 possible numbers each

The number of possible numbers that can take the place of the 10th digits = 9 possible numbers each

The total number of possible numbers is given as follows;

9 × 9 × 10⁶ × 9 = 729000000 possible student numbers