Problem
Six triangle pieces A meet in the center to make the hexagon. Each piece A has size 1, so the triangles together cover 6 x 1 = 6.
Six equal pieces of size 1 add to 6 by simple repeated addition.
4.MD.A.3Make A Systematic ListFour square pieces B are attached around the hexagon. Each piece B has size about 2, so the squares together cover about 4 x 2 = 8.
Four pieces of size 2 each add to 8, again just multiplying a count by a size.
4.MD.A.3Make A Systematic ListThe whole size is the triangle total plus the square total: 6 + 8 = 14.
Combining the area from triangles and squares gives the full shape's size.
4.OA.A.3Identify SubproblemsThe whole shape's area is the triangle pieces' total plus the square pieces' total, which is 6 + 8 = 14.
The shape is covered by these pieces alone, with no gaps and no overlaps, so its whole area is exactly all the piece areas added together.
Those piece areas add up as two subtotals, 6 from the triangles and 8 from the squares, which are then combined.
Regrouping which amounts you add first never changes a sum, so the triangles may be totaled together and the squares together before the two are added.
The triangle subtotal is 6 because six equal pieces of size 1 make six groups of one, the same as adding one six times.
The square subtotal is 8 because four equal pieces of size 2 make four groups of two, the same as adding two four times.
Add up the size of every block: six size-1 triangles plus four size-2 squares makes about 14 -- just counting and multiplying!