Question 2 • Probability and Statistics with Applications Honors Sem-2-FL-1210300 (2024-2025)
Because Renee’s and Thomas’s shell counts are independent, their total is approximately Normal with mean 58.2 + 47.9 = 106.1 and standard deviation √(12.8² + 11.5²) ≈ 17.2. For 120 shells, the z-score is (120 − 106.1) ÷ 17.2 ≈ 0.81. The probability of a total of 120 or more is the upper-tail probability, about 0.209, so the answer is 0.209.
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