Answer:
a.
MP3 player: 88%
Video game player: 92%
b.
MP3 player: 75 minutes
Video game player: 67 minutes
Explanation:
a.
MP3 player
- Already has 40%
- Each 15 minutes additional 12%
--> An hour = (60/15)*12 = 48 (%)
--> After an hour charged = 40 + 48 = 88%
Video game player
- Already has 20%
- Each 10 minutes additional 12%
--> An hour = (60/10)*12 = 72 (%)
--> After an hour charged = 20 + 72 = 92 (%)
b. To charges 100 minutes:
MP3 player
100 = 40 + ((x/15*12)
--> x = 75 (minutes)
Video game player
100 = 20 + ((x/10*12)
--> x = 67 (minutes)