Answer:
A = 90km2
Step-by-step explanation:
Area of a rhombus is:
1. A = s x h (if given side and height)
2. A = 1/2 a x b (if given lengths of diagonals)
3. A = s^2 sin A (if given side and length)
Therefore from your problem, height and side is given thus, you'll use number 1
A = s x h
A = 9km x 10km = 90km2
