The contents of a consignment of 1200 tins of a product have a mean mass of 0.504 kg and a standard deviation of 92 g. Determine the probability that a random sample of 40 tins drawn from the consignment will have a combined mass of
(a) less than 20.13 kg,
(b) between 20.13 kg and 20.17 kg,
(c) more than 20.17 kg, correct to three
significant figures.
The attached picture shows my attempt and answer for (a).I found a probability of 0.4801 but the book says the probability is 0.0179. How do they get this answer and what is wrong with what i did?
(a) less than 20.13 kg,
(b) between 20.13 kg and 20.17 kg,
(c) more than 20.17 kg, correct to three
significant figures.
The attached picture shows my attempt and answer for (a).I found a probability of 0.4801 but the book says the probability is 0.0179. How do they get this answer and what is wrong with what i did?
Attachments

63.7 KB Views: 4