Will you please provide me the Regional Mathematics Olympiad Exam Previous Years Question Papers????????

Here I am sharing the Regional Mathematics Olympiad Exam Previous Years Question Paper:

4. How many 6-digit numbers are there such that:
(a) the digits of each number are all from the set {1, 2, 3, 4, 5};
(b) any digit that appears in the number appears at least twice?
(Example: 225252 is an admissible number, while 222133 is not.)
Solution:
Since each digit occurs at least twice, we have following possibilities:
1. Three digits occur twice each. We may choose three digits from {1, 2, 3, 4, 5} in
(5
3ü= 10 ways. If each occurs exactly twice, the number of such admissible 6-digit
numbers is
6!
2! 2! 2! þ10 = 900.