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Question

The total population of a town is 50,000. The number of males and females increases by 10% and 15% respectively and consequently the population of the town becomes 56,000. What was the number of males in the town?

The correct answer is
30,000

Population Growth Calculation

Let the initial number of males be represented by M and the initial number of females by F.

Initial Population Setup

  • Total initial population: $M + F = 50,000$

Population Growth Details

  • Males increase by 10%, so the new male population is $M + 0.10M = 1.10M$.
  • Females increase by 15%, so the new female population is $F + 0.15F = 1.15F$.
  • The final total population is given as 56,000.

Therefore, the equation for the final population is: $1.10M + 1.15F = 56,000$

Solving for Initial Males

We have a system of two linear equations:

  1. $M + F = 50,000$
  2. $1.10M + 1.15F = 56,000$

From equation (1), express $F$ in terms of $M$: $F = 50,000 - M$

Substitute this expression for $F$ into equation (2): $1.10M + 1.15(50,000 - M) = 56,000$

Distribute and simplify:

  • $1.10M + 57,500 - 1.15M = 56,000$
  • Combine the terms with $M$: $-0.05M + 57,500 = 56,000$

Isolate the term with $M$: $-0.05M = 56,000 - 57,500$ $-0.05M = -1,500$

Solve for $M$: $M = \frac{-1,500}{-0.05}$ $M = 30,000$

The initial number of males in the town was 30,000.

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Important Questions from Percentage (Notes)

  1. 20% of a number is more than 20% of 620 by 210. The number is:
  2. Girish scored 572 marks in an examination and was 30 marks short of 28% of maximum marks. In the same examination, his friend scored 473 marks. What is the percentage of marks scored by his friend?
  3. Anubhav spent 14% of his income on electricity bills, 28% on rent and 18% on shopping. If $\frac{1}{4}$ th of the remaining amount is ₹5120, how much did he spend on electricity bills ?
  4. There is an increase of 30% in the number of people coming to a theatre after reducing the entry fee by 25% per person. How much change is expected in the total earnings?
  5. Gokul donates $17\%$ of his savings to old age home, $17\%$ of the savings to orphanage and $17\%$ of his savings to foundations for medical help. The remaining amount of Rs.$9800$ of savings is been deposited in bank. Find the salary of Gokul, if $50\%$ of the salary is his savings amount. (In Rs.)
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