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.