1. **Problem:** The area of a trapezium is 34 cm², one parallel side is 10 cm, and the height is 4 cm. Find the length of the other parallel side. 2. **Formula:** The area $A$ of a trapezium with parallel sides $a$ and $b$ and height $h$ is given by: $$A = \frac{1}{2} (a + b) h$$ 3. **Given:** - Area $A = 34$ cm² - One parallel side $a = 10$ cm - Height $h = 4$ cm - Other parallel side $b = ?$ 4. **Substitute values into the formula:** $$34 = \frac{1}{2} (10 + b) \times 4$$ 5. **Simplify:** $$34 = 2 (10 + b)$$ 6. **Divide both sides by 2:** $$\frac{34}{2} = 10 + b$$ $$17 = 10 + b$$ 7. **Solve for $b$:** $$b = 17 - 10 = 7$$ **Answer:** The length of the other parallel side is $7$ cm.