Town population grows from one value to another in some years: population after another period

The same question, asked 3 times: 9 May 2023 S1*, 22 Apr 2025 S1*, 25 Apr 2025 S1. Every wording below, oldest first.

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Question 1
9 May 2023 S1
103 $The population of a town increases at a rate proportional to the population at that time. If the population increases from 40 thousand to 80 thousand in 40 years, then the population in another 40 years will be$
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Question 2
22 Apr 2025 S1
123 $The population of a town increases at a rate proportional to the population at that time. If the population increases from forty thousand to eighty thousand in 20 years, then the population in another 40 years will be$
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Question 3
25 Apr 2025 S1
104 $The rate at which the population of a city increases varies as the population. In a period of 20 years, the population increased from 4 lakhs to 6 lakhs. In another 20 years the population will be$
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Question 1