ABCD is a rectangle with a length of 8 cm and a breadth of 5 cm. If AC is diagonal, then what is the area of triangle ACD?

Given,

The length of a rectangle = 8 cm

The breadth of a rectangle = 5 cm

Area of triangle ACD = $\frac{1}{2}$(Area of rectangle ABCD)

= $\frac{1}{2}(\mathrm{length}\times \mathrm{breadth})$

= $\frac{1}{2}(8\times 5)$

= $\frac{1}{2}\times 40$

= 20 cm²

Therefore, the area of the triangle ACD is 20 cm².