

It was the hottest day of summer. Penny, Sam, and Lily ran to Sunny Park. "Let's get popsicles!" shouted Sam. They saw Mr. Cool's colorful cart. Many children crowded around it. "I want cherry!" said one child. "Grape for me!" said another. Mr. Cool's face looked worried. "I only have twelve popsicles left," he said. "And twenty children are waiting!" The line grew longer and longer. Penny watched closely.

Mr. Cool announced, "Popsicles are two dollars today instead of one dollar." Some children left the line. Others stayed. The popsicles sold out in minutes. Penny didn't get one. "Why did the price go up?" she asked Mr. Cool. He smiled at her question. "Many people wanted popsicles, but I didn't have enough. When lots of people want something and there isn't much, the price goes up," he explained. Penny nodded thoughtfully.

The next day was cool and cloudy. Penny, Sam, and Lily returned to the park. Mr. Cool had his cart full of popsicles. "I brought fifty popsicles today!" he said cheerfully. But only five children came to buy them. Hours passed. Most popsicles remained in the cart. "Today popsicles are only fifty cents," announced Mr. Cool. "Why so cheap?" asked Lily. "I have many popsicles, but not many customers," Mr. Cool explained.

Mr. Cool drew a see-saw in the dirt. "Imagine supply on one side and demand on the other," he said. "When demand goes up and supply is low, prices rise like yesterday." He tipped the see-saw. "When supply goes up and demand is low, prices fall like today." Penny's eyes lit up. "I understand! It's like a balance!" The friends each bought a popsicle. "Now I know why prices change," Penny said proudly. Economics was actually fun!