Interpreting Rate of Change and the Constant Amount (KEY)

The average lifespan of American women has been tracked, and the model for the data isy= 0.2t+ 73, wheret= 0corresponds to 1960. Explain the meaning of the rate of change and the constant.

Rate of Change / Constant
VALUE: / 0.2 / 73
ABSTRACT: / As the (input, domain, independent) value t increases by 1, the (output, range, depend) value y increases by 0.2. / When t = 0, y = 73.
Or
Initially the output is 73.
RELATED: / Every year the average lifespan of American women increased by 0.2 years. (~ 2 months and 12 days) / In 1960 (when they started counting), the average lifespan for an American woman was 73 years old.

The equation for the speed (not the height) of a ball that is thrown straight up in the air is given byv= 128 – 32t, wherevis the velocity (in feet per second) andtis the number of seconds after the ball is thrown. With what initial velocity was the ball thrown? What is the meaning of the rate of change?

Rate of Change / Constant
VALUE: / -32 / 128
ABSTRACT: / As the (input, domain, independent) value t increases by 1, the (output, range, depend) value v decreases by 32. / When t = 0, v = 128.
Or
Initially the output is 128.
RELATED: / Every second the velocity (speed) decreases by 32 ft/s. / The ball was released or launched upward with an initial velocity of 128 ft/s.

Fishermen in the Finger Lakes Region have been recording the dead fish they encounter while fishing in the region. The Department of Environmental Conservation monitors the pollution index for the Finger Lakes Region. The model for the number of fish deaths "y" for a given pollution index "x" isy= 9.607x+ 111.958. What is the meaning of the R.O.C.? What is the meaning of theconstant?

Rate of Change / Constant
VALUE: / 9.607 / 111.958
ABSTRACT: / As the (input, domain, independent) value x increases by 1, the (output, range, depend) value y increases by 9.607. / When x = 0, y = 111.958
Or
Initially the output is 111.958
RELATED: / For every increase in the pollution index by one unit, there are nine or ten more fish deaths each year. / If the pollution index was zero (no pollution or pure water), there would still be about 112 fish deaths a year anyway.