Problem
In chemistry lab, students started with $150.13 \mathrm{~g}$ of a substance. They were to heat the substance and reweigh it after $5,10,15$, and 20 minutes had passed and record the weights. The students recorded the following data: \begin{tabular}{|c|c|} \hline minutes passed & grams left \\ \hline 5 & 149.65 \\ \hline 10 & 123.93 \\ \hline 15 & 100.22 \\ \hline 20 & 89.96 \\ \hline \end{tabular} If the students round each weight measurement to the nearest tenth, what is the approximate total change in weight of the substance after 20 minutes?
Solution
Step 1 ：Subtract the initial weight from the weight after 20 minutes: $150.13 \mathrm{~g} - 89.96 \mathrm{~g} = 60.17 \mathrm{~g}$
Step 2 ：The approximate total change in weight of the substance after 20 minutes is $60.17 \mathrm{~g}$
