Question

During one year, the population of a locality increases by 5% but during the next year, it decreases by 5%. if the population at end of the second year was 7980, find the population at the beginning of the first year.

Answer 1

let, first year population was 100
After one year population 105
after two year population 95*105/100=19*21/4

If 2nd year's population is 19*21/4 than 1st year=100
if " " 7980 than 1st year population=100*4*7980/19*21=8000

Answer 2

Answer:

8000

Step-by-step explanation:

let the population at the beginning of the year be = x

after 1 year it is = x*105/100 = 105x/100 = 21x/20

after 2 year it is = 21x/20 * 95/100 = 399x/400

therefore,

399x/400 = 7980

or, x = (7980*400)/399 = 8000