The perimeters of two circular fields C1 and C2 are 40π m and 96π m, respectively. What is the radius of a third circular field C3 whose area is equal to the sum of the areas of C1 and C2?

A technician works with two square plates of side lengths 42 cm and 35 cm. From their combined area, a square portion with a side length of 28 cm is removed. What is the remaining area in cm2?

A square and a rectangle have the same perimeter. The length of the rectangle is twice its width. If the side of the square is 12 meters, what is the difference between the area of the square and the area of the rectangle?