Each battery will die when the remaining charge is 0 %.
The tablet's battery lasts longer. See solution.
Practice makes perfect
To determine which battery lasts longer, we can compare the number of hours it takes for each battery to have a 0 % charge. We will begin by finding when the laptop's battery dies from the given graph.
Notice on the graph that the laptop's battery charge reaches p=0 at t=5. This means that the laptop's battery lasts for 5 hours.
The Tablet
Next we will determine how long the tablet's battery lasts. It is given that the tablet's initial charge is 75 % and that the battery loses 12.5 % each hour. We can write each of these percents in decimal form as 0.75 and 0.125, respectively. Now we can use this information to write a linear equation in slope-intercept form.
p=0.75-0.125t
To graph this function, we will make a table of values.
Notice on the graph that the tablets's battery charge reaches p=0 at t=6. This means that the tablet's battery lasts more than 6 hours. Therefore, the tablet lasts longer than the laptop. To check our answer, we can substitute 0 for p into the tablet's battery equation and solve for t.
