This math topic focuses on the area of a part circle, specifically calculating the total circle area from the area of a shaded sector, given as a fractional part of the whole in decimal form. Each problem provides the area of a half-circle sector and asks to find the full circle area, practicing skills in geometric reasoning, fraction-to-decimal conversion, and area calculations within circle geometry. The questions include multiple-choice answers, all presenting opportunities to apply geometric concepts in a practical context.