711, A MATHEMATICAL PUZZLEA customer walks into a 711 store and picks up four items. How much do I pay?  she asks. The clerk punches a few numbers on a calculator as the customer watches on.  That will be exactly $7.11 The customer raises her brows.  Excuse me but didn't you just MULTIPLY the four prices, instead of adding them...?  Oh, yes, I'm sorry! Just a minute...  says the clerk and this time adds the prices.  Here it is... $7.11  ???  Your four items add up to $7.11.  Well, here it is, but I guess I'll have to check myself ...  Sure, if anything is wrong please come back.  What are your opening hours?  711. [A long time ago 711 stores were open from 7am to 11pm.] QUESTION 1: What were the prices? QUESTION 2: Could that mistake have occurred with fewer or more than 4 items?

Those who solved the puzzle first (Andreas Andersson and Luiz Borgonovo) received a free lunch, worth... $7.11