1. **State the problem:** We are given two numbers, say $x$ and $y$, with the product $xy = ab$. We want to find the increase in the product when the first number $x$ is increased by 4. 2. **Set up the expression:** The original product is $xy = ab$. 3. **Increase the first number by 4:** The new first number is $x + 4$. 4. **Calculate the new product:** The new product is $(x + 4)y$. 5. **Find the increase in the product:** Increase = New product $-$ Original product $$\text{Increase} = (x + 4)y - xy = xy + 4y - xy = 4y$$ 6. **Express the increase in terms of $a$ and $b$:** Since $xy = ab$, we have $y = \frac{ab}{x}$. Therefore, $$\text{Increase} = 4y = 4 \times \frac{ab}{x} = \frac{4ab}{x}$$ **Final answer:** The increase in the product when the first number is increased by 4 is $$\frac{4ab}{x}$$.