# John received a score of 75 on a math test where the mean was 50. If his score is 2.5 standard deviations away from the mean, what is the variance of the classes test scores?

In John's case he is 25 away from the mean, which translates to 2.5 times the standard deviation $\sigma$. So:
$\sigma = \frac{25}{2.5} = 10 \to \text{variance} = {\sigma}^{2} = 100$