As everything gets more expensive, how do we balance the need to treat ourselves while on break with the need to make sensible choices? CNA's Melissa Lee weighs in. SINGAPORE: We’ve all heard of girl math . But the practice of young women justifying purchases with lighthearted unconventional logic is nowhere near as dangerous as its older, less conspicuous cousin: Travel math. Recently, I took a blockbuster of a trip: London the first week, Amsterdam the next, and then New York for the last