New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    A bowl contains a colony of bacteria. Every hour, the

    bacteria population doubles, but immediately after doubling, a virus kills 40% of the population. After 3 hours, the population of bacteria in the bowl is found to be 4320. What was the initial population of bacteria in the bowl?
    A 2500 Correct Answer Incorrect Answer
    B 2000 Correct Answer Incorrect Answer
    C 1500 Correct Answer Incorrect Answer
    D 3000 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let the population of bacteria in the beginning be '100x' So, population at the end of 1st hour = 100x X 2 X 0.6 = '120x' So, population at the end of 2nd hour = 120x X 2 X 0.6 = '144x' So, population at the end of 3rd hour = 144x X 2 X 0.6 = '172.8x' ATQ: 172.8x = 4320 So, x = 25 So, population of the bacteria in the beginning = 100x = 100 X 25 = 2500

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