A battery that lasts for 12 hours has been in use for 7 hours. What percent of the battery life has been used up?

To find out how much of the battery life has been used, you can use the formula: \( \text{Used Percentage} = \left( \frac{\text{Time Used}}{\text{Total Time}} \right) \times 100 \). In this case, plug in the numbers: \( \text{Used Percentage} = \left( \frac{7}{12} \right) \times 100 \), which equals approximately 58.33%. So, about 58.33% of the battery life has been used up! As a fun fact, battery technology has come a long way! In the early days of batteries, like the very first wet cell batteries invented by Alessandro Volta in the early 1800s, they could barely hold a charge for a few hours. Now, we have lithium-ion batteries that power everything from smartphones to electric cars, giving us significantly longer usage times!