The original version of this story appeared in Quanta Magazine. Imagine a town with two widget merchants. Customers prefer cheaper widgets, so the merchants must compete to set the lowest price.

The simple interest formula is Interest = P * R * T. Many, or all, of the products featured on this page are from our advertising partners who compensate us when you take certain actions on our ...

Julia Kagan is a financial/consumer journalist and former senior editor, personal finance, of Investopedia. Xavier Lorenzo / GettyImages If you're looking for a loan, finding the most affordable ...

Carol M. Kopp edits features on a wide range of subjects for Investopedia, including investing, personal finance, retirement planning, taxes, business management, and career development. Betsy began ...

Interest rates are a key feature of many credit cards and play a big part in the potential fees you may be charged for carrying a balance. If you already carry a balance on your credit card, you're ...

High-interest debt has a bad reputation — and rightfully so. Debt that charges high rates is the most expensive for borrowers to carry. And the longer you leave it unpaid, the quicker the costs grow, ...

WASHINGTON, DC - JULY 30: Federal Reserve Chairman Jerome Powell answers questions from reporters following the regular Federal Open Market Committee meetings at the Fed on July 30, 2025 in Washington ...

Use this student loan interest calculator to understand how much you're really paying for college each month. Many, or all, of the products featured on this page are from our advertising partners who ...

In major reversal, the odds of a December interest rate cut have risen to 79% from around 40% earlier this month. The jump in expectations came after New York Fed President John Williams said further ...

Evan Coleman is an Updates Editor on the Credit Cards and Travel Rewards team at Forbes Advisor, showcasing his interest in personal finance and love of travel. He has written for a variety of local ...