This is a problem with a non-linear equation. The data is the temperature of water and the time. But we have to fit a line anyway.
We can the Least Squares Method, the best line fit is:
[tex]\begin{gathered} y=mx+b \\ m=\frac{n\sum ^{}_{}(x\cdot y)-\sum ^{}_{}x\cdot\sum ^{}_{}y}{n\sum ^{}_{}x^2-(\sum ^{}_{}x)^2} \\ b=\frac{\sum ^{}_{}y-m\sum ^{}_{}x}{n} \\ \text{where n is the number of points} \end{gathered}[/tex]
Now, we apply the formula above:
[tex]m=\frac{10\cdot2072.5-22.5\cdot880}{10\cdot71.25-22.5^2}=\frac{20725-19800}{712.5-506.25}=\frac{925}{206.25}=4.48[/tex]
