Final answer:
A change in the price of a good alters the quantity demanded, in accordance with the law of demand. A price increase typically leads to lower demand, whereas a price decrease tends to increase demand.
Step-by-step explanation:
A change in the price of a good changes the quantity demanded. This concept is captured by the law of demand, which states that there is an inverse relationship between price and quantity demanded. For example, when the price of a gallon of gasoline rises, people may reduce consumption by combining errands or using alternative transportation.
Conversely, a decrease in price generally increases quantity demanded. The extent of this effect can be influenced by individual preferences and purchasing power.