Question: In order to be accepted into the Olympic team, candidates must score withing the top 10% on the final qualification test. Given that the test scores are normally distributed with a mean of 100 and a standard deviation of 20, what is the lowest possible score a candidate needs to be accepted?  Edit

Answer: OK, first you need to go to a z-chart and find the z-score needed to be in the top 10% of a normal distribution. If you look at a chart, you'll see that the z-score is 1.28. Remember:
z = (x - mean)/standard deviation
1.28 = (x - 100)/20
25.6 = x - 100
125.6 = x

The lowest possible score is 125.6  Edit