Nina's grades could be better. She gets about five hours of sleep every weeknight and ten hours per night on weekends. How much sleep should she get to better concentrate on schoolwork? five to six hours every night nine to ten hours every night a total of forty hours a week a minimum of eighty hours a week Save and Exit Next Mark this and return

The correct option is;

A total of forty hours a week

Step-by-step explanation:

The given information in the question are;

The number of hours of sleep Nina gets during weeknights = five hours

The number of hours of sleep Nina gets per night on weekends = ten hours

The number of days in a week = 5 days

The number of days in a weekend = 2 days

Therefore;

The number of hours of sleep Nina gets per week = 5 days × 5 hours/day + 2 days × 10 hours/day

∴ The number of hours of sleep Nina gets per week = 25 hours + 20 hours = 45 hours

The number of hours of sleep Nina gets per week = 45 hours

To better concentrate on schoolwork, Nina could get a total of forty hours a week of sleep a week to increase the number of hours she spends weekly on her schoolwork by up to 5 hours (45 hours - 40 hours).

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step-by-step explanation: