A) Daily sales of petrol from the Nabua service station are normally distributed with Mean 6300L and the standard deviation 400L.

(i) If a daily sale is selected at random, find the probability that it is less than 6200L.
(ii) If petrol sales are sampled for 40 days, and the mean is calculated, find the Probability that the sample mean is less than 6200L.
(iii) Define the Central limit theorem

6200-6300 divided by 400 to get the z-score. Then use the z-table to find the probability of less than you z-score or you could use a stat calculator like at TI-83 or 84 to find the probability.

For forty days you have to use 400 divided by the square root of 40 as the standard deviation.
repeat the problem, but use the new standard deviation

You can find the definition in your text or a simple google search.