In 1972 federal vehicle emission standards allowed 3.4 hydrocarbons released per mile driven. By 2007 the standards allowed only 0.8 hydrocarbons per mile driven. What was the rate of change from 1972 to 2007?

Answer 1

(0.8-3.4)/(2007-1972) = -2.6/35 = -0.074 (hc/mile)/year

if you want a % yearly rate, then that would be -0.77%/year

Answer 2

Since it’s talking about rate of change you want to take 3.4-0.8 to get 2.6