A random variable Y is normally distributed with a mean of 100 and a standard deviation of 10. What is the probability that Y is less than 90 or greater than 110?

So, we are looking for the probability that $Y$ is less than one standard deviation below the mean or greater than one standard deviation above the mean.

The Empirical Rule states that for a normal distribution, approximately 68% of the data falls within 1 standard deviation of the mean.
This means $P(\mu - \sigma < Y < \mu + \sigma) \approx 0.68$.
In our case, $P(90 < Y < 110) \approx 0.68$.

The probability that $Y$ is less than 90 or greater than 110 is the complement of the probability that $Y$ is between 90 and 110.

Comparing this result with the given options:

a) 0.15

b) 0.32

c) 0.68

d) 0.84

e) 0.95

The calculated probability matches option (b).

The final answer is $\boxed{\text{b) } 0.32}$.