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Mathematics

Statement 1: The population of a town in the year 2024 is x and it increases by 10% every year. The population of in the year 2021 was = x (110100)3\Big(1 - \dfrac{10}{100}\Big)^3

Statement 2: If the population increases from year 2021 to year 2024 at the rate of 10%, then corresponding decrease from 2024 to 2021 is 10 x 3%.

  1. Both the statements are true.

  2. Both the statements are false.

  3. Statement 1 is true, and statement 2 is false.

  4. Statement 1 is false, and statement 2 is true.

Compound Interest

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Answer

The general formula for population growth with a fixed annual percentage increase is:

Pt = Po (1+r100)t\Big(1 + \dfrac{r}{100}\Big)^t

where, Pt = Population after t years

P0 = Initial population

r = Annual growth rate (in percentage)

t = Time in years

Given, the population in 2024 is x, and the annual growth rate is 10%. To find the population in 2021, we need to go back 3 years (from 2024 to 2021).

Rearranging the formula to solve for P0 = Pt(1+r100)t\dfrac{P_t}{\Big(1 + \dfrac{r}{100}\Big)^t}

⇒ P0 = x(1+10100)3\dfrac{x}{\Big(1 + \dfrac{10}{100}\Big)^3}

So, statement 1 is false.

If the population increases from year 2021 to year 2024 at the rate of 10%.

Let P0 be the population in 2021 and Pt be the population in 2024.

⇒ Pt = P0 (1+10100)3\Big(1 + \dfrac{10}{100}\Big)^3

⇒ Pt = P0 (1 + 0.1)3

⇒ Pt = P0 x 1.13

⇒ Pt = 1.331P0

The percentage decrease = PtPoPt×100\dfrac{Pt - Po}{P_t} \times 100

=1.331PoPo1.331Po×100=0.331Po1.331Po×100=3311331×10024.87%= \dfrac{1.331Po - Po}{1.331Po} \times 100\\[1em] = \dfrac{0.331Po}{1.331P_o} \times 100\\[1em] = \dfrac{331}{1331} \times 100\\[1em] ≈ 24.87\%

So, statement 2 is false.

∴ Both the statements are false.

Hence, option 2 is correct option.

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