Answer: A. $32$

Explanation:1. Identify the given equation: $5x = 4$

2. Identify what needs to be found: The value of $40x$.

3. Solve for $x$ or find a relationship between $5x$ and $40x$: Method 1: Solve for $x$. - Divide both sides of the given equation by $5$: $x = \dfrac{4}{5}$ - Substitute this value of $x$ into the expression $40x$: $40x = 40 \times \left(\dfrac{4}{5}\right)$ $40x = \dfrac{40 \times 4}{5}$ $40x = \dfrac{160}{5}$ $40x = 32$

Method 2: Find a multiplicative factor. - We want to transform $5x$ into $40x$. - To get from $5x$ to $40x$, we multiply by $8$ (since $5 \times 8 = 40$). - Multiply both sides of the given equation $5x = 4$ by $8$: $8 \times (5x) = 8 \times 4$ $40x = 32$

4. Compare with the given options (Source 331): - [A] $32$ (Matches our result) - [B] $12$ - [C] $28$ - [D] $4$

5. Conclusion: The value of $40x$ is $32$.