Excel in math and science
Master concepts by solving fun, challenging problems.
It's hard to learn from lectures and videos
Learn more effectively through short, interactive explorations.
Used and loved by over 7 million people
Learn from a vibrant community of students and enthusiasts,
including olympiad champions, researchers, and professionals.
Excel in math and science
Master concepts by solving fun, challenging problems.
It's hard to learn from lectures and videos
Learn more effectively through short, interactive explorations.
Used and loved by over 7 million people
Learn from a vibrant community of students and enthusiasts,
including olympiad champions, researchers, and professionals.
Problems of the Week
Contribute a problem- Week of December 17
- Week of December 10
- Week of December 3
- Week of November 26
- Week of November 19
- Week of November 12
- Week of November 5
- Week of October 29
- Week of October 22
- Week of October 15
- Week of October 8
- Week of October 1
- Week of September 24
- Week of September 17
- Week of September 10
- Week of September 3
- Week of August 27
- Week of August 20
- Week of August 13
- Week of August 6
- Week of July 30
- Week of July 23
- Week of July 16
- Week of July 9
- Week of July 2
- Week of June 25
- Week of June 18
- Week of June 11
- Week of June 4
- Week of May 28
- Week of May 21
- Week of May 14
- Week of May 7
- Week of April 30
- Week of April 23
- Week of April 16
- Week of April 9
- Week of April 2
- Week of March 26
- Week of March 19
- Week of March 12
- Week of March 5
- Week of February 26
- Week of February 19
- Week of February 12
- Week of February 5
- Week of January 29
- Week of January 22
- Week of January 15
- Week of January 8
- Week of January 1
- Week of December 25
- Week of December 18
- Week of December 11
- Week of December 4
- Week of November 27
- Week of November 20
- Week of November 13
- Week of November 6
- Week of October 30
- Week of October 23
- Week of October 16
- Week of October 9
- Week of October 2
- Week of September 25
- Week of September 18
- Week of September 11
- Week of September 4
- Week of August 28
- Week of August 21
- Week of August 14
- Week of August 7
- Week of July 31
- Week of July 24
- Week of July 17
- Week of July 10
- Week of July 3
- Week of June 26
- Week of June 19
- Week of June 12
- Week of June 5
- Week of May 29
- Week of May 22
- Week of May 15
- Week of May 8
- Week of May 1
- Week of April 24
- Week of April 17
- Week of April 10
- Week of April 3
- Week of March 27
- Week of March 20
- Week of March 13
- Week of March 6
- Week of February 27
- Week of February 20
- Week of February 13
- Week of February 6
Why does this toy always bounce back no matter how hard it's punched?
by
Rohit Gupta
Are you sure you want to view the solution?
The segments dividing this triangle are parallel to the triangle's base.
Which colored area is the largest?
by
Hana Wehbi
Are you sure you want to view the solution?
What is the radius of this quarter-circle?
by
Gergő Dénes
Are you sure you want to view the solution?
A small ball is placed on top of a bigger, heavier ball at a height of 10 m above the ground.
When the balls are simultaneously released and bounce, how high will the smaller ball bounce up to?
Assumptions:
- All collisions are perfectly elastic, which means no kinetic energy is lost in the collisions.
- Air resistance is negligible.
by
Pranshu Gaba
Are you sure you want to view the solution?
Which of the following figures has the greatest area shaded in red?
Assumptions:
- A, B, C are identical equilateral triangles. The circles of A are all congruent to each other, as are the circles of C.
- The red components are circles tangent to one another and to the triangle.
Note: If you get it wrong, don't worry! An Italian mathematician named Malfatti also got it wrong in the 19th century.
by
Andrei Li
Are you sure you want to view the solution?