Harder concepts from Mathcounts Mini :
Also try the follow-up problems with detailed solutions. Don't do every question. Just the ones you think is hard.
Geometry :
#27 : Area and Volume
#30: Similar Triangles and Proportional Reasoning
#34: Circles and Right Triangles
#35: Using Similarity to Solve Geometry Problems
#41: Analytic Geometry : Center of Rotation
From Mathcounts Mini : Video tutorials on counting and probability for Mathcounts state/national prep
concepts are in the of difficulty.
Counting the Number of Subsets of a Set
Constructive Counting
More Constructive Counting
Probability and Counting
Probability with Geometry Representations : Oh dear, the second half part is hilarious.
Probability with Geometry Representations : solution to the second half problem from previous video
Try this one from 1998 AIME #9. It's not too bad.
Also try the follow-up problems with detailed solutions. Don't do every question. Just the ones you think is hard.
Geometry :
#27 : Area and Volume
#30: Similar Triangles and Proportional Reasoning
#34: Circles and Right Triangles
#35: Using Similarity to Solve Geometry Problems
#41: Analytic Geometry : Center of Rotation
From Mathcounts Mini : Video tutorials on counting and probability for Mathcounts state/national prep
concepts are in the of difficulty.
Counting the Number of Subsets of a Set
Constructive Counting
More Constructive Counting
Probability and Counting
Probability with Geometry Representations : Oh dear, the second half part is hilarious.
Probability with Geometry Representations : solution to the second half problem from previous video
Try this one from 1998 AIME #9. It's not too bad.