You can read posting Sarin learns Perimeter, Area and Volume in school(Math Concept) to learn the concept of perimeter, area and volume.
Read also the posting on Sarin learns Shapes and Solids in school (Math Concept) to know about shapes.
You should also click and read the posting on Sarin learns the concept of Fraction (mathematics concept) to understand Portion or Fraction.
Upper primary school mathematics question UPQ145
The figure consists of 2 squares and a circle. What fraction of the figure is shaded in yellow?
Take the radius as r
The area of the outer square = 2r × 2r
The shaded square can be subdivided as 2 identical triangles with the breadth = 2r and the height = r
The area of the triangle = ½ × 2r × r
The area of the inner square = r × 2r
The fraction of the figure is shaded = r × 2r / 2r × 2r = ½