Final answer:
To calculate the number of oysters the manager should expect to open to find two pearls of the appropriate size, we use the concept of the normal distribution with the mean diameter of 8 millimeters and standard deviation of 2 millimeters.
Step-by-step explanation:
To calculate the number of oysters that the manager should expect to open to find two pearls of the appropriate size, we need to use the concept of the normal distribution. The mean diameter of pearls in the oyster bed is 8 millimeters and the standard deviation is 2 millimeters. We can use the properties of the normal distribution to determine the probability of finding a pearl within the specified range, which is between 7 and 9 millimeters.
First, we calculate the z-scores for the lower and upper limits of the range. The z-score is calculated with the formula: z = (x - μ) / σ, where x is the value we are interested in, μ is the mean, and σ is the standard deviation.
So for the lower limit, z = (7 - 8) / 2 = -0.5, and for the upper limit, z = (9 - 8) / 2 = 0.5.
Next, we use a z-table or calculator to find the probabilities associated with these z-scores. The probability of finding a pearl within the specified range is then the difference between these two probabilities.
Finally, to find the expected number of oysters to open to find two pearls, we divide the total number of oysters by the probability of finding a pearl within the specified range.