Sharon and Ken just finished a wonderful meal at a fancy restaurant. The service and food were five-star quality. Ken asked for the check. "How much is the tip?" Sharon asked. Since she and Ken were just friends, she didn't want him to pay for the whole meal, but since Ken did invite her, she assumed he was paying. Sharon thought that offering to put in the tip was a nice gesture. The tip was not going to be cheap. The meal, complete with a bottle of wine, must have been at least $200. $30 would be 15 percent of a $200 bill, and $40 would be 20 percent of a $200 check. Since the service was good, Sharon had no problem giving a 20 percent tip.