Since approximately 68% of a (roughly) normal distribution falls within one standard deviation of the mean, that leaves 32% that falls outside, and by symmetry 16% should lie above one standard deviation of the mean.
A negative times a negative is a positive. I am not sure if that's the question, but hopefully that helps if it was.
Answer:
45 mins
Step-by-step explanation:
The question is how much time should the painter spend on painting a doll for the costs to still be equal or lower to $24.50
We can make this equation, representing the raw materials + the painting job (at $18/h):
$11 + $18x = $24.50
18x = 13.50
x = 13.5 / 18 = 0.75
So, the painter should spend at most 3/4 of an hour (or 45 mins) painting a doll to keep the cost at or below $24.50 per doll.