This mathematical problem can be solved by using the rule of three, which involves finding an unknown value by using three related values. The process is shown below:
1. It is known a fully charged battery (100% battery) lasts 16 hours. This can be represented as 100 = 16. But it is not know how much a 30% battery last; this can be represented as 30 = x.
2. Write all the values
100 = 16
30 = x
3. Cross multiply to create an equation and solve the equation
