Answer:
[tex]{ \rm{rate \: of \: change = \frac{R _{2}(t) - R _{1}(t) }{t _{2} - t _{1}} }} \\ [/tex]
For 0 < t < 10; 226.6 < R(t) < 205.6
[tex]{ \rm{ = \frac{205.6 - 226.6}{10 - 0} }} \\ \\ { \rm{ = - \frac{21}{10} }} \\ \\ = { \rm{ - 2.1}} \\ \\ = 2.1[/tex]
Negative indicates an inverse proportionality, or decrease in temperature
For 30 < t < 50; 157.6 < R(t) < 119.6
[tex] = { \rm{ \frac{119.6 - 157.6}{50 - 30} }} \\ \\ = { \rm{ - \frac{38}{20} }} \\ \\ = { \rm{1.9}}[/tex]
