Americans have loved McDonald’s Quarter Pounder ever since a franchisee introduced the iconic burger to the country in 1972. In the 1980s, A&W attempted to capitalize on the success of the Quarter Pounder—and drum up a little competition for Ronald and friends—by introducing a third-pound burger. The bigger burger gave consumers more bang for their collective buck. It was priced the same as the Quarter Pounder but delivered more meat. It even outperformed McDonald’s in blind taste tests, with consumers preferring the flavor of A&W’s burger.

But when it came down to actually purchasing the third-pound burgers, most Americans simply would not do it. Baffled, A&W ordered more tests and focus groups. After chatting with people who snubbed the A&W burger for the smaller Quarter Pounder, the reason became clear: Americans suck at fractions. Alfred Taubman, who owned A&W at the time, wrote about the confusion in his book Threshold Resistance:

More than half of the participants in the Yankelovich focus groups questioned the price of our burger. "Why," they asked, "should we pay the same amount for a third of a pound of meat as we do for a quarter-pound of meat at McDonald's? You're overcharging us." Honestly. People thought a third of a pound was less than a quarter of a pound. After all, three is less than four!

Not understanding that a fourth is actually smaller than a third, many consumers eschewed the better-tasting burger in favor of the one they thought was the better deal. According to Taubman, A&W recalibrated their marketing, saying, “The customer, regardless of his or her proficiency with fractions, is always right.”

Apparently undaunted by the average American’s less-than-average math skills, McDonald’s tried their own version of the bigger burger, the “Angus Third-Pounder,” in 2007.

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It didn’t last, but they gave it another shot with the “Sirloin Third Pounder” just last year. That one is gone now, too, but the mighty Quarter Pounder remains a mainstay.