# Tag Archives: Combinatorics

## [Soln] 2013 AIME I Problem 6

2013 AIME I 6. Melinda has three empty boxes and 12 textbooks, three of which are mathematics textbooks. One box will hold any three of her textbooks, one will hold any four of her textbooks, and one will hold any five of … Continue reading

## 2013 AIME I Problem 6

2013 AIME I 6. Melinda has three empty boxes and 12 textbooks, three of which are mathematics textbooks. One box will hold any three of her textbooks, one will hold any four of her textbooks, and one will hold any five of … Continue reading

## [Soln] 2013 AIME I Problem 4

2013 AIME I 4. In the array of 13 squares shown below, 8 squares are coloured red, and the remaining 5 squares are coloured blue. If one of all possible such colourings is chosen at random, the probability that the chosen coloured array appears … Continue reading

## 2013 AIME I Problem 4

2013 AIME I 4. In the array of 13 squares shown below, 8 squares are coloured red, and the remaining 5 squares are coloured blue. If one of all possible such colourings is chosen at random, the probability that the chosen coloured array appears … Continue reading

## [Soln] 2013 AIME I Problem 2

2013 AIME I 2. Find the number of five-digit positive integers, , that satisfy the following conditions: (a) the number is divisible by 5, (b) the first and last digits of are equal, and (c) the sum of the digits of … Continue reading