Robert, Julie, and Erin went to a cafe on a weekend. Their shared bill came to $25. Each person gave the server a $10 bill. The server took
this $30 and brought back five $1 bills in change. Each person took $1
back, leaving the rest, $2, as a tip for the server.
As he walked away from the cafe, Robert thought, "Wait—this doesn't
make sense. Since I put in $10 and got $1 back, I wound up paying $9.
So did Julie and Erin. Together, we paid $27. Then we left a $2 tip. That
makes $29 total. And yet we originally gave the waiter $30. Where did
the extra dollar go?"
Think about the situation and about Robert's question. Do you agree
that the numbers didn't add up properly? Explain your reasoning on the
next slide.