Area of Triangles and Parallelograms Worksheets - Math Monks - Free Printable

Let’s solve each problem one by one. We’ll use the correct formulas:

- Area of a triangle = (base × height) ÷ 2
- Area of a parallelogram = base × height

We must make sure we’re using the perpendicular height — not just any side!

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Triangles (Problems 1–6)

Problem 1:
Base = 12 cm, Height = 3 cm
Area = (12 × 3) ÷ 2 = 36 ÷ 2 = 18 cm²

Problem 2:
Base = 8.5 in, Height = 7 in
Area = (8.5 × 7) ÷ 2 = 59.5 ÷ 2 = 29.75 in²

Problem 3:
Base = 9 cm, Height = 4 cm
Area = (9 × 4) ÷ 2 = 36 ÷ 2 = 18 cm²

Problem 4:
This is a tricky one — the height given (6.6 cm) is perpendicular to the side labeled 8.2 cm. So that side is the “base” for this calculation.
Area = (8.2 × 6.6) ÷ 2
First: 8.2 × 6.6 = let’s compute:
8 × 6.6 = 52.8
0.2 × 6.6 = 1.32
Total = 52.8 + 1.32 = 54.12
Then divide by 2: 54.12 ÷ 2 = 27.06 cm²

Problem 5:
Base = 8.2 in, Height = 4.4 in
Area = (8.2 × 4.4) ÷ 2
Compute 8.2 × 4.4:
8 × 4.4 = 35.2
0.2 × 4.4 = 0.88
Total = 35.2 + 0.88 = 36.08
Divide by 2: 36.08 ÷ 2 = 18.04 in²

Problem 6:
Base = 12 yd, Height = 9 yd
Area = (12 × 9) ÷ 2 = 108 ÷ 2 = 54 yd²

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Parallelograms (Problems 7–12)

Problem 7:
Base = 8 cm, Height = 4 cm (perpendicular to base)
Area = 8 × 4 = 32 cm²

Problem 8:
Base = 10 cm, Height = 6 cm
Area = 10 × 6 = 60 cm²

Problem 9:
Base = 6 cm, Height = 3 cm
Area = 6 × 3 = 18 cm²

Problem 10:
Base = 16 yd, Height = 8 yd
Area = 16 × 8 = 128 yd²

Problem 11:
Base = 11 m, Height = 9 m
Area = 11 × 9 = 99 m²

Problem 12:
Base = 21.4 in, Height = 16.6 in
Area = 21.4 × 16.6
Let’s calculate carefully:
21 × 16.6 = 21 × 16 + 21 × 0.6 = 336 + 12.6 = 348.6
0.4 × 16.6 = 6.64
Total = 348.6 + 6.64 = 355.24
So area = 355.24 in²

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Final Answer:
1. 18 cm²
2. 29.75 in²
3. 18 cm²
4. 27.06 cm²
5. 18.04 in²
6. 54 yd²
7. 32 cm²
8. 60 cm²
9. 18 cm²
10. 128 yd²
11. 99 m²
12. 355.24 in²