3. A simple model of the core of a tornado is a right circular cylinder that rotates about its axis. If a tornado has a core diameter of 200 feet and maximum wind speed of 180 mi/hr (or 264
ft/sec) at the perimeter of the core, approximate the number of revolutions the core makes
each minute.

In this exercise we have to use knowledge about probability to calculate the probability of faster time, so we have to:

probability that Yuki's time is faster than Zana's.

When the distribution is normal, we use the z-score formula. In a set with mean  and standard deviation , the zscore of a measure X is given by:

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X.

Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

Find the probability that Yuki's time is faster than Zana's. That is, the subtraction of Yuki's time by Zana's time has to be higher than 0. When we subtract normal distributions, the mean is the subtraction of the means. So:

The standard deviation is the square root of the sum of the variances. So:

We have to find 1 subtracted by the p-value of Z when X = 0. So:

Has a p-value of 0.7611:

See more about probability at link