Question

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emma’s e - reader can work for 7 hours reading books or 28 hours on standby. after reading for 2 hours and leaving it on standby for 8 hours, emma has used of the battery.

Explanation:

Step1: Find reading battery rate

Rate = $\frac{1}{7}$ per hour

Step2: Find standby battery rate

Rate = $\frac{1}{28}$ per hour

Step3: Calculate used reading battery

Used = $2 \times \frac{1}{7} = \frac{2}{7}$

Step4: Calculate used standby battery

Used = $8 \times \frac{1}{28} = \frac{2}{7}$

Step5: Sum total used battery

Total = $\frac{2}{7} + \frac{2}{7} = \frac{4}{7} = \frac{1}{2}$

Answer:

$\frac{1}{2}$