Helpful video links below from Math Antics:
Area http://mathantics.com/index.php/section/lesson/Area
What is Pi? http://mathantics.com/index.php/section/lesson/Circles_WhatIsPI
Circumference and Area of Circles
http://mathantics.com/index.php/section/lesson/Circles_CircumferenceAndArea
CCSS: Solve real-life and mathematical problems involving angle measure,
area, surface area, and volume. 4. Know the formulas for the area and circumference of a circle and use them to solve problems; give an informal derivation of the relationship between the circumference and area of a circle. 6. Solve real-world and mathematical problems involving area, volume and surface area of two- and three-dimensional objects composed of triangles, quadrilaterals, polygons, cubes, and right prisms.