Area of shaded portions

Question

Find the areas of the shaded portions of the figures below. Give answers to 2 decimal places if necessary.

A)Circle in a square (shaded part) with sides of W=10cm and L=10cm

B) Two triangles (shaded part) in a rectangle touching tip to tip, one on the top and another on the bottom with:
W= 10CM
L=20CM

Answer 1

A) Assuming the circle is tangent to the square at the square's four sides, the diameter of the circle is 10cm, which means its radius is 5cm. A = pi * r² = pi * (5cm)² = 78.54 cm².

 

B) I'm not sure about this one because your description was not very clear. But I am going to assume that the base of the triangle is the width of the rectangle (if not, then just switch the length and width in all of the following calculations. The area of a triangle is 0.5 * b * h. I am going to assume the two triangles are the same size. Then the total area = 2 * 0.5 * b * h = b * h. The height of one triangle is half the length of the rectangle, or h = 0.5 * L = 0.5 * 20cm = 10cm. The base of one triangle is just the width of the rectangle = 10cm. Then A = 10cm * 10cm = 100 cm².