Here triangles ABC and ADC are congruent
ar (∆ABC) = ar (∆ADC)
Also triangles ABC and ADC have equal perimeters.
Therefore, area of rhombus ABCD
= 2 x area of ∆ABC = 2 x 432
= 864 m2
Also area of grass field each cow will graze
= \(\frac { 864 }{ 18 }\) m2 = 48 m2.