C. 895. The series of diagrams shown is made up of more and more dark regular triangles. The series is continued to the n-th diagram according to the rule that can be observed. How many dark triangles are used altogether?
Google Translation (Sorry, the solution is published in Hungarian only.)
Megoldás. A sötét háromszögek száma:
Statistics on problem C. 895. 211 students sent a solution.
5 points:118 students.
4 points:8 students.
3 points:8 students.
2 points:16 students.
1 point:26 students.
0 point:10 students.
Unfair, not evaluated:25 solutions.