The times of the runners in a marathon are normally distributed, with a mean of 3 hours and 50 minutes and a standard deviation of 30 minutes. What is the probability that a randomly selected runner has a time less than or equal to 3 hours and 20 minutes? Use the portion of the standard normal table below to help answer the question.zProbability0.000.50000.500.69151.000.84132.000.97723.000.9987

Convert the times to minutes: 3 hours 50 minutes is 230 minutes, and 3 hours 20 minutes is 200 minutes. The z-score is (200 − 230) ÷ 30 = −1, so the runner’s time is one standard deviation below the mean. The table gives a probability of 0.8413 for a z-score of 1; by symmetry, the probability below −1 is 1 − 0.8413 = 0.1587, or about 16%. The correct choice is A, 16%.

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