The number of pages per book on a bookshelf is normally distributed with mean 248 pages and standard deviation 21 pages. Using the empirical rule, what is the probability that a randomly selected book has less than 206 pages?

The probability is 0.0228

Step-by-step explanation:

We proceed by calculating the z-score value

Mathematically;

z-score = (x - mean)/SD

where x = 206, mean = 248 and SD = 21

Substituting these values, we have;

z-score = (206-248)/21 = -42/21 = -2

So the probability we want to calculate is;

P(z < -2)

We can use the standard normal distribution table for this;

P(z < -2) = 0.0228

because linear equations are a lot simpler than quadratics equations, and linear equations formula is a lot easier to memorize. that's why i think they're harder.