Final answer:
The horizontal axis on a total product curve represents the quantity of inputs. This graph helps in understanding the relationship between inputs and the output in production, showing how output changes as we change input quantities.
Step-by-step explanation:
When we draw a total product curve, the horizontal axis typically represents the quantity of inputs used in the production process. This type of graph is particularly useful for understanding the relationship between these inputs (like labor, machinery, and raw materials) and the resulting output of goods or services produced by a firm. As we increase the number of inputs on the horizontal axis, the total product curve shows how the total output of the firm changes, helping to illustrate concepts such as increasing, constant, or decreasing returns to scale.