Gas prices are dropping across the state of Tennessee and nationally.Since Monday, the national average per gallon of gasoline has dropped a nickel as crude oil dips below $100 a barrel. In the Volunteer State, the average price of gas is $3.18, which is down 24 cents from last year this time. Locally, News 2 found the cheapest gas to be at Dodge's in Clarksville at $2.98 per gallon. Experts expect the gas prices to continue to fall in coming weeks. Click here for the lowest gas prices in your area.