Question

town has population of 50,000 in 1988. In one year i.e. by 1989 it increased by 25%. Next year i.e. in 1990, it decreased by 30%. The next year in 1991 there was an increase of 40%. What is the population at end of 1991?​

Answer 1

Answer:

61250

Step-by-step explanation:

1988 -- 50000

1989 -- 25% increase = 50000*(100+25)/100= 62500

1990 -- 30% decrease = 62500*(100-30)/100= 43750

1991 -- 40% increase = 43750*(100+40)/100= 61250

Answer is 61250

Answer 2

Step-by-step explanation:

Given: Population in 1988, and percentage increase in population in 1989,1990 and 1991.

To find: Population at end of 1991.

For calculation of population at end of 1991,

We know that population in 1988 $(P)=50,000$

We know that rate of increase in 1989 $(R1)= 25$%

We know that rate of increase in 1990 $(R2)=30$%

We know that rate of increase in 1991 $(R3)= 40$%

$Time=3$ years, and Population in 1991 $=A$

∴ $A=P (1+\frac{R1}{100})$ × $(1-\frac{R2}{100})$ × $(1+\frac{R3}{100})$

⇒ $50,000$ × $(1+\frac{25}{100})$ × $(1-\frac{30}{100})$ × $(1+\frac{40}{100})$

⇒ $50,000$ × $\frac{125}{100}$  × $\frac{70}{100}$  × $\frac{140}{100}$

⇒ $5$  × $125$ × $7$ × $14$

⇒ $61,250$

The population at end of 1991 is $61,250$.