Gas was 17 cents a gallon in 1931 so you could have bought a gallon of gas with 1.7 dimes back then. If you had those same silver dimes today they’d buy 2 gallons of gas.
Just a little reminder: Don’t think of things in terms of that phony paper money that isn’t backed by anything. That stuff is only useful as a quick mechanism to trade with. Temporarily convert into that phony paper to buy or sell something, then get back out of it. Real money is gold and silver.
Note my message board avatar (PIC).