Gas prices have dropped again across Montana just as drivers hit the roads for one of the year's busiest travel times.GasBuddy.com reports average gasoline prices in the state have fallen 4.2 per gallon in the last week and are averaging $2.79 per gallon as of Monday.Gas prices are 20.2 per gallon lower than at this time a month ago and 22.7 per gallon lower than a year ago. The national average price of gasoline has risen 3.1 per gallon over the last week to $3.01 per gallon, which is 2.6 lower than a month ago.GassBuddy.com reports the cheapest gas in Montana was at $2.56 per gallon on Sunday while the most expensive was $3.06 per gallon.