Answer
$0.90$ pounds per kilo
Work Step by Step
The average rate of change of $f(x)$ over the interval $[a, b]$ is $\displaystyle \frac{f(b)-f(a)}{b-a}$
Units: "(unit of f(x) ) per (unit of x)"
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Given the interval $[1,3]$ and the table,
a=$1,\ \quad C(1)=2.20$
b=$3,\ \quad C(3)=4.00$
$\displaystyle \frac{C(b)-C(a)}{b-a} =\displaystyle \frac{4.00-2.20}{3-1}$
$=\displaystyle \frac{1.80}{2}=0.90$ ( pounds per kilo)
