Week 232 (21 January 2022)

Simon picks a 4-digit number at random.

The first digit is not a zero.

The 4-digit number is a multiple of 5.

How many different 4-digit numbers could Simon pick?


There are 9 possibilities for the first digit, 10 for the second and third and 2 for the last.

By the Product Rule for Counting:

Total number of ways =   9 x 10 x 10 x 2  = 1800.