Question 437912
1. The grade, or slope is simply the rise over the run:
Slope = rise/run = 7/11 = 0.64
2. Given A = -3t + 980
Since 1995 is 5 years after 1990, we substitute the value 5 in the equation
A(5) = -3(5) + 980 = 965 million acres
For the year 2000 we have:
A(10) = -3(10) + 980 = 950 million acres
And for 2010:
A(20) = -3(20) + 980 = 920 million acres
From 1990, when A = 980 to 2010 when A = 920 the change was 60 million acres in 20 years.
Therefore the rate of change is 60/20 = 3 million acres per year
Of course, we also can see this from the slope of the equation, -3.