Imagine walking into your favorite coffee shop. You notice the price of a latte has jumped by a dollar. Do you shrug and order anyway, or does it make you reconsider your caffeine fix? This decision is at the heart of elasticity—a measure of how much quantity demanded or supplied reacts to changes in price.

Elasticity isn't just about price tags. It reveals how deeply intertwined products are in your life. That's the answer to the opening puzzle: avocados are easy to skip or swap for another topping, so demand is elastic — a price spike sends shoppers scrambling elsewhere. Gasoline, on the other hand, often remains in your budget regardless of price leaps because substitutes are scarce and you need it to get around.