The Average Rate of Change is the change of the function's value to the change in the variable t along some close interval
[tex]f(t) = 1.1~t^2 - 2.5t + 1.5\\~\\f(5)=1.1~(5)^2 - 2.5(5) + 1.5=16.5\\~\\~\\f(3)=1.1~(3)^2 - 2.5(3) + 1.5=3.9\\~\\~\\ARC= \frac{f(5)-f(3)}{5-3} = \frac{16.5-3.9}{5-3} =6.3[/tex]
I hope that
helps!