Question 1180209
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Use your 68-95-99.7 rule to get the answer.<br>
69-55=14=2(7); 55 degrees is 2 standard deviations below the mean.<br>
76-69=7; 76 degrees is 1 standard deviation above the mean.<br>
68% of readings are within 1 standard deviation of the mean, so 34% of readings are between the mean and a reading 1 standard deviation above the mean.  So in this problem 34% of the readings are between 69 and 76 degrees.<br>
95% of readings are within 2 standard deviations of the mean, so 47.5% of readings are between the mean and a reading 1 standard deviations below the mean.  So in this problem 47.5% of the readings are between 55 and 69 degrees.<br>
So the percentage of readings between 55 and 76 degrees is 34+47.5=81.5%.<br>
ANSWER d.<br>