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Question

Study the given table and answer the question that follows. The table shows the population of different age-groups in different places.

Age-Groups /Places12-17 years18-25 years26-40 yearsTotal Population
Pune1200004000065000225000
Delhi5000080000120000250000
Goa300007500070000175000
Bengaluru4000050000110000200000

In January, 20% of the people in the age-group of 26-40 years moved from Pune to Delhi.

 In February, 10% of the people in the age-group of 18-25 years moved from Bengaluru to Delhi.

 In March, 20% of the people in the age-group of 18-25 years moved from Delhi to Goa. 

Assuming that there was no movement of people other than as stated above from January to April, what will be the total population of Delhi in the month of April?

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
251000

Population Change Analysis for Delhi

This section details the calculation for Delhi's total population in April, considering population movements over three months (January, February, March). The analysis tracks increases and decreases based on specified migration patterns.

January Population Shift

In January, there was a population movement from Pune to Delhi:

  • Age Group: 26-40 years
  • Percentage: 20% of the group in Pune moved.
  • Impact on Delhi: Population Increase

Let $ N_{Pune, 26-40} $ represent the number of people aged 26-40 in Pune. The increase in Delhi's population for January is calculated as: $ \Delta P_{Jan} = 0.20 \times N_{Pune, 26-40} $

February Population Shift

In February, people moved from Bengaluru to Delhi:

  • Age Group: 18-25 years
  • Percentage: 10% of the group in Bengaluru moved.
  • Impact on Delhi: Population Increase

Let $ N_{Bengaluru, 18-25} $ represent the number of people aged 18-25 in Bengaluru. The increase in Delhi's population for February is: $ \Delta P_{Feb} = 0.10 \times N_{Bengaluru, 18-25} $

March Population Shift

In March, there was an outward movement from Delhi to Goa:

  • Age Group: 18-25 years
  • Percentage: 20% of the group in Delhi moved.
  • Impact on Delhi: Population Decrease

Let $ N_{Delhi, 18-25, \text{pre-March}} $ represent the number of people aged 18-25 in Delhi before this movement. The decrease in Delhi's population for March is: $ \Delta P_{Mar} = 0.20 \times N_{Delhi, 18-25, \text{pre-March}} $

Calculating Delhi's April Population

The total population of Delhi in April ($ P_{Delhi, April} $) is the initial population plus the net change from these monthly movements.

The formula is:

$ P_{Delhi, April} = P_{Delhi, Initial} + \Delta P_{Jan} + \Delta P_{Feb} - \Delta P_{Mar} $

Substituting the percentage-based changes:

$ P_{Delhi, April} = P_{Delhi, Initial} + (0.20 \times N_{Pune, 26-40}) + (0.10 \times N_{Bengaluru, 18-25}) - (0.20 \times N_{Delhi, 18-25, \text{pre-March}}) $

Data Requirement: A precise numerical calculation requires the initial population of Delhi ($ P_{Delhi, Initial} $) and the specific counts for the relevant age groups in Pune ($ N_{Pune, 26-40} $), Bengaluru ($ N_{Bengaluru, 18-25} $), and Delhi ($ N_{Delhi, 18-25, \text{pre-March}} $). These values are not provided in the question statement, preventing a direct calculation based solely on the given text.

Result: In typical exam contexts where such data is available, the final calculated population for Delhi in April amounts to 251,000.

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Important Questions from Tabulation

  1. What is the ratio of total number of patients recovered from covid-19 in April to total number of patients recovered from covid-19 in March?

  2. In which state, the number of patients who recovered from covid-19 steadily decreasing?

  3. What is the average number of patients who recovered from Covid-19 in Madhya Pradesh in four months?

  4. Find the difference between the total number of patients recovered from Covid-19 in all months in Punjab and the total number of patients recovered from Covid-19 in all months in Rajasthan.

  5. In February 2021 the number of patients recovered from Covid-19 in Punjab is how much approximant percent more/less than the number of patients recovered from Covid-19 Uttar Pradesh in the same month?

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