Your answer would be 50 cm².
This is because the formula for finding the area of a kite is (p × q)/2, where p and q represent the diagonals of the kite.
This means we need to do (10 × 10)/2, as 5 + 5 = 10 so that is the total of that diagonal, and we are told that the total of the vertical diagonal is 10. (10 × 10)/2 = 100/2 = 50.
I hope this helps!