Combinatorics

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

id: 14543

How many of the numbers in 0,1,2,...,999 have a first digit equal to 1 or 9?

id: 14616

In a restaurant the guests can choose a main out of 4 pizzas and 3 pastas. How many main courses are there?

id: 14520

How many of the numbers in 0,1,2,...,999 have at least one digit equal to 9?