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Percentage: Population Growth Rate
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This lesson is all about population increase and decrease and its application to solve question using shortcut.

## Bharat Gupta is teaching live on Unacademy Plus

Bharat Gupta
An engineer by degree Mathematician by Heart. Having 23 years of teaching experience. 10% discount code BHARAT_GUPTA

U
Great explanation!!!
AG
Sir, please make a video on checking the options and the divisibility rule (4:37)
Dear sir in 7.56 time, for cement question, if we use the smart approach that is multiplication factor approach we will get 144.5 %, which will be wrong hence can not go for the smart approach. We can only use successive percentage method that is xy method.
why we need to divide by 23
UC
Unknown Caller
2 months ago
because 115 is multiple of 23 or 23 is factor of 115. So if any number is divisible by 23, that number must be divisible by 115.
The value of a property depreciates every year by 10% of its value at the beginning of the year. The present value of the property is Rs. 8100. What was its value 2 years ago?
Vinay NR Vinav
4 months ago
i think 9802
sir i would like to know that how 6-2.16 = 3.84
1. Percentage Lesson Part 5 Population Problems

2. Er, Bharat Gupta Having 20 years of teaching experience. Authored several books published by Pearson, Vikas, Unique publication etc Any query or suggestion, share your comments. . .

3. Population Population appreciation or depreciation follows Compound interest pattern. Compound interest pattern means when percent increase or decrease always calculated on current value. Formula Appreciation Formula r t Let present population of certain city P Rate of appreciation (Growth rate)-1% Population after t years = Pt Pt = Po(1+100) o Depreciation Formula Let present population of certain city = Po Rate of depreciation (Decrease rate)-1% Population after t years P r t Pt- Pt = Po (1-100 P0 |

4. Population growth using Multiplication Factor Population of a city increase at the rate of 10%. If we use formula for this than the value of population after (let) 3 years would be 3 10 100 100 + 103 Step 1 P3 = Po I-100 Step -2 3 110 100 P3-Po Step-3 P3 = Po(1.1)3 Step-4 Here 1.1 is multiplication factor

5. Population growth using Multiplication Factor Population of a city increase at the rate of 10%. If we use formula for this than the value of population after (let) 3 years would be 3 10 100 100 + 103 Always use Multiplication Factor For solving question like this Step -1 P3 = Poll+ Ps= Po( 100 Ps = Po (100 P3 = Po(1.1)3 Calculation of Multiplication Factor (M.F Population increase Add 100 to rate and put two decimal from Right hand side If rate is 15 % then Mf. = 100 15 = 115 = 1.15 Population decrease Subtract 100 to rate and put two decimal from Right hand side If rate is 12 % then M.F = 100-12 = 88 = 0.88 Step -2 3 3 110 Step-3 3 Step-4 Here 1.1 is multiplication factor

6. Population increase and decrease Application If the annual increase in the population be 15% and present population be 20,000. What will be the population after 2 years a. 28800 b. 26450 c. 25088 d. 24200

7. If the annual increase in the population be 15% and present population be 20,000. What will be the population after 2 years a. 28800 b. 26450 c. 25088 d. 24200 por,Jahon o 2Xa.s Po r mg ,. MA2

8. The population of a city in the first two year increase by 20% and in the next year decrease by 15%. If current population be 25000 then the population after 3 years a. 28800 b. 29700 c. 30600 d. 18400

9. The population of a city in the first two year increase by 20% and in the next year decrease by 15%. If current population be 25000 then the population after 3 years a. 28800 b. 29700 c. 30600 d. 18400

10. The annual production in cement industry is subject to business cycles. The production increases for two consecutive years consistently by 18% and decreases by 12% in the third year. Again in the next two years, it increases by 18% each year and decreases by 12% in the third year. Taking 2008 as the base year, what will be the approximate effect on cement production in 2012? a. 24% increase c.45% increase [IIFT (2012)] b.37% decrease d. 60% decrease