Clearly, the diagonal AC of the rhombus divides it into two congruent triangles.

For triangle ABC, a = b = 30 m, c = 48 m.
∴ s = a +b + c/ 2 = 30 +30 + 48 /2 m = 54 m

∴ Area of the rhombus = 2 × 432 m2 = 864 m2
Number of cows = 18
Hence, area of the grass field which each cow gets
= 864/ 18 m2 = 48 m2 Ans.