A person is born every 5 seconds and a person dies every 12 seconds. How many seconds does it take for the population to grow by one person?
Correct answer: B. 8 4⁄7 sec
- A. 7 sec
- B. 8 4⁄7 sec
- C. 10.5 sec
- D. 10 5⁄7 sec
Explanation
Time it takes for the population to grow by one person = "x" seconds.In "x" seconds, the number of people born would be "x/5" and the number of people who died would be "x/12".So the net increase in the population would be:x/5 - x/12We want this net increase to be equal to 1, since we are interested in finding the time it takes for the population to grow by one person.Therefore, we can set up the equation:x/5 - x/12 = 1Multiplying both sides by the least common multiple of 5 and 12, which is 60, we get:12x - 5x = 60Simplifying:7x = 60x = 60/7 secondsWe can convert this into a mixed number to get:x = 8 4/7 secondsTherefore, the answer is (B) 8 4/7 seconds.
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