Question

. The population of a city increases at the rate
of 5% every 5 years. If 15 years ago, it was
160000, what is the population now?​

Answer 1

Given:

P=185220,R=5% (increases) and n=3yr.

According to the formula ,

Population n yr ago = P/ (1+r/100)^n

185220/ (1+5/100)³= 185220 × 20 × 20 × 20/ 21 × 21× 21

20 × 20 × 20 × 20 = 160000

Answer 2

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The population of a city increases at the rate of 5% every 5 years. If 15 years ago, it was 160000, what is the population now?

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Given :-

Rate of increment = 5%

Present population = 185220

Formula used :-

Population after each increment = x × (100 + r)/100

where, x = initial population, r = rate of increment.

Calculations :-

Let the population of the city three years before be x, then

x × (105/100) × (105/100) × (105/100) = 185220

⇒ x = 185220 × (20/21) × (20/21) × (20/21)

⇒ x = 160000

∴ The population 3 years back of the city are 160000.