A village has 4000 literate people in the year 2010 and this number increases by 400 per year. How many literate people will be there till the year 2020 ? Find a formula to know the number of literate people after n years ?


5. A village has 4000 literate people in the year 2010 and this number increases by 400 per year. How many literate people will be there till the year 2020 ? Find a formula to know the number of literate people after n years ?

Sol. Since the no. of literate people increases by 400 every year, the population of literate people every year forms an A.P.

No. of people in the year 2010 (a) = 4000

Increase in population every year (d) = 400

No. of years from 2010-2020 (n) = 10

tn = a + (n – 1) d

 t10 = 4000 + (10 – 1) 400
 t10 = 4000 + 9 (400)
 t10 = 4000 + 3600
 t10 = 7600

 There will be 7600 literate people till the year 2020

tn = a + (n – 1) d
 tn = 4000 + (n – 1) 400
 tn = 4000 + 400n – 400
 tn = 3600 + 400n

There will be (3600 + 400n) literate people after n years.