# Model 8 Population Based Practice Questions Answers Test With Solutions & More Shortcuts

#### PERCENTAGE PRACTICE TEST [11 - EXERCISES]

Question : 1 [SSC CGL Tier-II 2015]

From 1980-1990, the population of a country increased by 20%. From 1990-2000, the population of the country increased by 20%. From 2000-2010, the population of the country increased by 20%. Then the overall increased population (in percentage) of the country from 1980-2010 was

a) 60 %

b) 72.2 %

c) 72.8 %

d) 62.8 %

Using Rule 7,

If a number is first increased by a% and then again increased by b%, then total increase percent is \$(a + b + {ab}/100)%\$

Single equivalent increase for 20% and 20%

= \$(20 + 20 + {20 × 20}/100)%\$ = 44%

Single equivalent increase for 44% and 20%

= \$(44 + 20 + {44 × 20}/100)%\$

= (64 + 8.8)% = 72.8%

Question : 2 [SSC CGL Prelim 2003]

The present population of a city is 180000. If it increases at the rate of 10% per annum, its population after 2 years will be :

a) 227800

b) 207800

c) 217800

d) 237800

Using Rule 17,

If the population/cost of a certain town/ article, is P and annual increament rate is r%, then

1. After ‘t' years population/cost = \$P(1 + r/100)^t\$
2. Before ‘t' years population/cost = \$P/{(1 + r/100)^t}\$

Required population after two years = \$180000(1 + 10/100)^2\$

= \$180000 × 11/10 × 11/10 = 217800\$

Question : 3 [SSC Constable 2013]

Raman's salary is increased by 5% this year. If his present salary is Rs.1,806, the last year's salary was

a) Rs.1620

b) Rs.1720

c) Rs.1520

d) Rs.1801

Using Rule 17,

Required Raman's salary = \$100/{100 + 5} × 1806\$

= \$100/105 × 1806\$ = Rs.1720

Question : 4 [SSC CGL Prelim 2008]

The population of a town increases every year by 4%. If its present population is 50,000, then after 2 years it will be

a) 54,000

b) 53,900

c) 54,080

d) 54,900

Using Rule 17,

Required population = \$50000(1 + 4/100)^2\$

= \$50000 × 26/25 × 26/25\$= 54080

Question : 5 [SSC CHSL 2015]

An epidemic broke out in a village in which 5% of the population died. Of the remaining, 20% fled out of panic. If the present population is 4655, then the population of the village originally was

a) 6125

b) 6000

c) 5955

d) 5995

Using Rule 28,

Population after ‘n' years = \$P(1 ± R_1/100)(1 ± R_2/100)…(1 ± R_n/100)\$

Original population of village = x (let)

According to the question,

\$x × 95/100 × 80/100 = 4655\$

\$x = {4655 × 100 × 100}/{95 × 80}\$ = 6125

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