Final answer:
A store credit is shown as a negative number because it indicates an obligation or liability that the store owes to a customer, much like a negative displacement indicates movement in the opposite direction in mathematics.
Step-by-step explanation:
A store credit is represented by a negative number because it signifies an amount that the store owes to the customer, rather than the customer owing to the store. In accounting terms, this is considered a liability for the store, as it is money that will have to be 'paid out' in the form of goods or services in the future, instead of received payment. Therefore, in the store's financial statements, it appears as a negative figure, reducing the overall balance.
Just as in mathematics, where subtracting a larger number from a smaller number results in a negative value, a store credit reduces the amount of money that a store can claim as its revenue. Hence, it's similar to the way distance can be negative when displacement is in the opposite direction of the chosen positive reference point, as illustrated by the example of Komal's displacement being -100 m relative to his house and school.
Essentially, the negative sign indicates that the transaction has moved in the opposite direction to a typical sale - rather than money coming into the store, it represents money that will go out of the store when the credit is used. This is analogous to the mathematical rules where negative numbers indicate movement in the opposite direction or a subtraction from a total.