A country has a current annual population growth rate of 2 percent. Using the rule of seventy, the approximate time required for its population to double is:
- A 25 years
- B 35 years ✓
- C 50 years
- D 70 years
Correct answer: B. 35 years
Explanation
By the rule of seventy, doubling time in years is obtained by dividing 70 by the annual percentage growth rate. Here 70 divided by 2 gives 35 years, making option B correct. Option A would correspond to a growth rate of nearly 2.8 percent, option C to 1.4 percent, and option D to exactly 1 percent. This shortcut is widely used to estimate how quickly a population with a constant growth rate will double in size.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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