barbie5878, hello
The diagonal of a quadrilateral "cuts" the quadrilateral into two triangles, with the base of each triangle being 26cm. The height of one triangle is 12.8cm and the height of the other triangle is 11.2 cm. Using the formula for the area of a triangle (A=1/2bh), we get:
The area of the quadrilateral is the sum of the areas of the two triangles, that is:
Area = (0.5)(26cm)(12.8cm) + (0.5)(26cm)(11.2cm) or
Area = 166.4 cm2 + 145.6 cm2 = 312 cm2
Please let me know if this helped.
