Civil Engineering - Water Supply Engineering - Discussion

5. 

The population of a city in 2000 is 50,000. The average increase in population over last 8 decades is 7500 and average incremental increase during 8 decades is 750. The population of the city based on incremental method, in the year 2020 will be

[A]. 55,000
[B]. 60,500
[C]. 66,500
[D]. 72,500
[E]. 76,500

Answer: Option C

Explanation:

No answer description available for this question.

Jajhjiik said: (Aug 14, 2015)  
According to incremental increase method, yn = yo+nr+n(n+1)/2xk.

yo = Initial population n = No of decades k = net incremental increase.

r = avg increase in population.

So, y 2020 = 50000+7500x2+3x750 = 67250.

Answer given is wrong.

Grace said: (Mar 29, 2017)  
By incremental increase method, Pn = P + n (Average Increase+ Incremental Increase)
Given: P=50,000 ; n=2 ; Average Increase = 7500 ; Incremental Increase = 750,
Hence P2=50000+2(7500+750) = 66,500.

Ghosh said: (Nov 14, 2017)  
Yes 67250 is the right answer here.

Satish Verma said: (Apr 18, 2018)  
67250 is the right option.

Jignesh said: (Sep 5, 2018)  
@Jajhjiik.

Can you please explain how came 2 ad 3?

Girma B. said: (Feb 26, 2019)  
The final answer is 67250.

Subhasmita Patra said: (Jul 14, 2019)  
The formula for geometrical increase method is;

P(1+IG/100)^n.

P= population.
IG= average percentage per decade.
n= no of decad.

So, Pn=50000(1+20/100)^2.
= 72000.

Mahesh Sinh said: (Mar 31, 2020)  
Pn = P+n(Ia+Iinc),
Pn = 5000+2(7500+750).
= 66500.

Prashanth said: (Apr 20, 2020)  
@Jajhjiik.

How it came 3? please explain sir.

Renis@Gajipara said: (Aug 26, 2020)  
The population of the city based on the incremental method, in the year 2020.

i = 7500 & r = 750.
Pn = P + (i+r)n.
= 50000 + (7500+750)*2.
Pn = 66500.

Where,
P = Present population in 2000.
i = avg. increase in population.
r = avg. incremental increase.
n = Number of decades.

Pooja said: (Sep 11, 2020)  
Pn = Po + nx + [(n(n+1))/2]*y.
n = no Of decades,
x = avg increase in population,
y = avg. incremental increase,
Po = initial population.

Anirban Roy said: (Sep 23, 2020)  
Yes, you are right @Pooja. So,

Pn = 55000 + 2 * 7500+(2 * 3รท2) * 750 = 67250.

Noini said: (Dec 3, 2020)  
Avg increase is 7500 calculated for 8 decades.

Then the total increase in population from 1930 is 7500x8=60000. If increase itself is 60000, what is the actual population in 1920 initially then? How can the population in 2000 be very less=50000?

Please anyone explain.

Smith said: (Dec 24, 2020)  
Thanks all for eplaining the answer.

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