Final answer:
The scenario that could be modeled using an inequality is determining the maximum weight allowed for luggage on an airplane, as it involves a maximum limit that should not be exceeded.
Step-by-step explanation:
The scenario that could be modeled using an inequality is A. Determining the maximum weight allowed for luggage on an airplane. Inequalities are used to represent situations where there is a range or limit, such as a maximum or minimum allowed. When dealing with the maximum weight allowed for luggage, we are typically given an upper limit that the weight must not exceed. For example, if the maximum weight allowed is 50 pounds, the inequality would be w ≤ 50, where w represents the weight of the luggage.
Other options, such as calculating the exact number of pencils in a pack or measuring the temperature of a boiling kettle, involve precise measurements or counts and would better be represented by equalities rather than inequalities. Counting the number of pages in a book is also a precise number and would not be an inequality.