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Q: The bacteria in a culture grow by 5% in the first hour, get destroyed by 5% in the second hour and again grow b 5% in the third hour. If the count of the bacteria at the end of the third hour is 8.379 * 108 , find the original count of bacteria in the sample.
A. 8*106 B. 8*104
C. 8*107 D. 8*108

Answer and Explanation


Let the original count be x. After the 1st hour , the count is x(1+5/100) = 1.05x. After the 2nd hour , the count is 1.05x(1 – 5/100) = 1.05(0.95)x. After the 3rd hour, the count is [1.05(0.95)x]( 1 + 5/100) = (1.05)(0.95) (1.05)x. Therefore, x= 8*108

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