1. **State the problem:** We need to find the area of a trapezoid with a curved top side, where the bottom base is 15 mm, the height is 6 units, and the top side length is 10 units. 2. **Formula for trapezoid area:** The area $A$ of a trapezoid is given by $$A = \frac{(b_1 + b_2)}{2} \times h$$ where $b_1$ and $b_2$ are the lengths of the two parallel sides (bases), and $h$ is the height. 3. **Important note:** Since the top side is curved, we approximate the area by treating the top side as a straight line of length 10 units. 4. **Apply the formula:** $$A = \frac{(15 + 10)}{2} \times 6$$ 5. **Simplify the expression:** $$A = \frac{25}{2} \times 6$$ 6. **Calculate the multiplication:** $$A = 12.5 \times 6$$ 7. **Final area:** $$A = 75$$ So, the approximate area of the trapezoid is 75 square units.