No, they are not going at the same speed. Because if you divided Train B’s time to get the speed of 1 minute, 90/5 you will get 18 miles in 1 minute. Which is 3 miles greater than Train A.
The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean and standard deviation , the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean and standard deviation .
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
For a proportion p in a sample of size n, the sampling distribution of the sample proportion will be approximately normal with mean and standard deviation
In this question:
We need to find n for which s = 0.09, with p = 0.66. So