Answer:
Ava's error is that she has calculated area using wrong formula. The correct formula for Area of Rectangle is Length x Width.
Using Ava's values of Length = 4 and Width = 6, the area of the rectangle is:
Area = Length x Width = 4 x 6 = 24 square units
Therefore, the correct area of the rectangle is 24 square units, not 10 as Ava calculated.