Combinatorics

Answer all the questions below and press submit to see how many you got right.

id: 14456

How many different even numbers smaller than 100 only contain digits between 1 and 3?

id: 14564

How many of the numbers in 1,2,3,...,427 are not divisible by 2?

id: 14516

How many of the numbers in 0,1,2,...,999 have at least one digit equal to 7?