This square piece of paper has been folded and creased. Where does the crease meet the side AD?

Weekly Problem 15 - 2015

In the diagram, two lines have been drawn in a square. What is the ratio of the areas marked?

What is the largest number of intersection points that a triangle and a quadrilateral can have?

Can you find the area of the triangle from its height and two sides?

In the diagram, the radius of the circle is equal to the length AB. Can you find the size of angle ACB?