Nabil has a tablet that starts with its battery fully charged to $100 \%$. The battery life decreases at a constant rate as the tablet is being used. He uses the tablet for exactly 60 minutes, after which $68 \%$ of the battery life remains. For how many more minutes can Nabil use the tablet before the battery is at $0 \%$ ?
Solution 1

Since the battery loses $100 \%-68 \%=32 \%$ every 60 minutes, the percentage of battery life after $t$ minutes is $P=100-\frac{32}{60} t$.

We can solve this equation for $P=0$ to get $t=\frac{100 \times 60}{32}=\frac{375}{2}$ minutes.

Since we are asked how long after the first hour ( 60 minutes) the battery will be at $0 \%$, the answer is $\frac{375}{2}-60=127.5$ minutes.

## Solution 2

The battery loses its charge at a rate of $100 \%-68 \%=32 \%$ every 60 minutes.

For the remaining $68 \%$ to disappear, it will take $\frac{68 \%}{32 \%} \times 60$ minutes, or $\frac{255}{2}=127.5$ minutes.

ANSWER: 127.5