gmattesttaker2 wrote:Hello,
Can you please tell me how to solve this:
In a certain country, a person is born every 3 seconds and a person dies every l0 seconds. Therefore, the birth and death rates account for a population growth rate of one person every:
A) 3 1/3 sec
B) 4 2/7 sec
C) 7 sec
D) 11 2/3 sec
E) 13 sec
OA: B
For the time, plug in the LCM of the two rates = 3*10 = 30 seconds.
Since a person is born every 3 seconds, the number of people born in 30 seconds = 30/3 = 10.
Since a person dies every 10 seconds, the number of people who die in 30 seconds = 30/10 = 3.
Net rate per 30 seconds = 10-3 = 7 people.
7 people per 30 seconds = 1 person per 30/7 seconds.
The correct answer is
B.
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