6 The mass of grapes sold per day by a large shop can be modelled by a normal distribution with mean 28 kg . On \(10 \%\) of days less than 16 kg of grapes are sold.
- Find the standard deviation of the mass of grapes sold per day.
The mass of grapes sold on any day is independent of the mass sold on any other day. - 12 days are chosen at random.
Find the probability that less than 16 kg of grapes are sold on more than 2 of these 12 days.
- In a random sample of 365 days, on how many days would you expect the mass of grapes sold to be within 1.3 standard deviations of the mean?