Gmat Probability
1. State the problem.
Most GMAT scores are normally distributed with mean $527$ and standard deviation $112$.
We are asked: what is the probability that a randomly selected individual scores above $500$?
2. Convert to a standard normal problem.
Use the z-score formula:
$$z = \frac{x-\mu}{\sigma}$$
Compute the z-score for $x=500$:
$$z = \frac{500-527}{112} = \frac{-27}{112} = -0.2410714286\text{ (approximately)}$$
3. Express the probability in terms of the standard normal distribution.
We want $P(X>500)=P\left(Z> -0.2410714286\right)$ where $Z$ is a standard normal random variable.
By symmetry of the standard normal distribution, $P\left(Z> -0.2410714286\right)=P\left(Z<0.2410714286\right)=\Phi\left(0.2410714286\right)$.
4. Evaluate the standard normal CDF value.
Using a standard normal table or calculator, $\Phi\left(0.2410714286\right) \approx 0.596053$.
5. Convert to percent and present the final answer.
Multiply by 100 to convert the probability to percent: $0.596053\times 100 \approx 59.6053$.
Round to two decimal places as requested to obtain the percent form without the percent symbol.
Final answer: 59.61