Randall B. answered 02/28/14
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Chemistry and Math (Everything up to Calculus I)
According to the problem, the patients survival rate doesn't start to decrease until the first 2 hours are up. By the end of the third hour, the patients survival rate is 85%. By the end of the 4th hour, the patients survival rate is now 72.25%.
(100%-15%)/100= 0.85
Third hour: 100% x (0.85) = 85%
Fourth hour: 85% x (0.85) = 72.25%
Or, depending on how you read into the question:
Third hour: 100% - 15% = 85%
Fourth hour: 85% - 15% = 70%