A rectangular paperboard measuring 21 in long and 16 in wide has a semi circle cut out of it, find the area of the paper board that remains

First you find the area of the semi circle. The semi circle would be considered a Sector Area of a circle. The formula to find that is (π (radius²) (given angle)) divided by 360. Assuming the semi circle goes across the width of the rectangle, it would be half of that measure. So 8 would be the radius. And the given angle would be 180 because it's a semi circle. You just plug that formula into ur calculator and get the answer 235.5in²