Answer:
Method 1
Find the area of the rectangle, 45 cm². Subtract the area of the cut-out triangle from the rectangle, 45 - 6 = 39 cm²
Method 2
Separate the ribbon into two triangles and a rectangle.
33 + 3 + 3 = 39 cm²
Explanation:
Formulae
- Area of a rectangle = width × length
- Area of a triangle = 1/2 × base × height
Method 1
Area of the rectangle:
= 3 × 15
= 45 cm²
Area of the cut-out triangle:
= 1/2 × 3 × 4
= 6 cm²
Find the area of the rectangle, 45 cm². Subtract the area of the cut-out triangle from the rectangle, 45 - 6 = 39 cm²
Method 2
Area of the rectangle:
= 3 × (15 - 4)
= 3 × 11
= 33 cm²
Area of one triangle:
= 1/2 × (3 ÷ 2) × 4
= 3 cm²
Separate the ribbon into two triangles and a rectangle.
33 + 3 + 3 = 39 cm²