James was doing some shopping at Walmart, when he came upon one of those handy signs advertising a price “Rollback” posted on a display of yogurt. But just because Walmart says something is a deal, it pays to do the math to make sure it actually is a bargain.

In this case, as James says, “I did the math, Walmart didn’t.” You could pay $0.58 for each yogurt, but Walmart is instead rolling prices “back,” which in this case means forward, and selling them at a rate of five for $3.00.

Calculator time, or just some simple brain power: At 58 cents each, five yogurts would normally cost $2.90. And hey, $2.90 is 10 cents less than $3.00! Check me out now, 7th grade math teacher who was always so disappointed in me!

James is also good at math, so he says he alerted a store employee to the odd “deal.” Unfortunately, this kind of thing is a pretty common story here at Consumerist.

I reported it to an assistant manager and she was amused until I pointed out I would probably be overcharged once I reached the register. Of course I was. Luckily I had this picture so we didn’t have to make the trip from the register to the back of the store to confirm the price.

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.