Polygon Splitter Anchor Chart
Math Toolkit: Geometry Grade 6-8 Reference
THE POLYGON SPLITTER
A step-by-step guide to decomposing irregular shapes into friendly formulas.
1
Slice It!
Draw dashed lines to split the irregular shape into rectangles or right triangles.
2
Label It!
Find missing side lengths. Opposites of a rectangle are equal!
3
Solve It!
Calculate the area of each smaller shape using friendly formulas.
4
Sum It!
Add all individual areas together to find the total area.
Square / Rectangle Area = length × width
Right Triangle Area = ½ × base × height
Method 1
Squares & Rectangles Only
A B 8m 4m 4m 10m w = 6m
1 & 2: Slice & Solve missing side
Missing width of B = 10m − 4m = 6m.
3: Solve individual areas
Area A 8 × 4 = 32m²
Area B 4 × 6 = 24m²
4: SUM BOTH AREAS A + B
32m² + 24m² = 56 m²
Method 2
Rectangles & Triangles
A B 5cm 6cm 5.8cm 9cm b = 3cm
1 & 2: Slice & Find missing base
Missing base of B = 9cm − 6cm = 3cm.
3: Solve individual areas
Area A 6 × 5 = 30cm²
Area B (Tri) ½ × 3 × 5 = 7.5cm²
4: SUM BOTH AREAS A + B
30cm² + 7.5cm² = 37.5 cm²
Don't Get Tricked!
Area units are always squared (e.g., m², cm²).
Ignore Extra Sides
Only use perpendicular height and base side lengths.
Opposites Match
Opposite parallel sides of a rectangle are always equal.