Question

their are 37 terms in ap sum of middle most term of an AP is 225 and sum od last 3 terms of an ap is 429 ,find ap

Answer 1

let a-d = 18
     a = 19
     a+d = 20
adding them we get
               3a = 225
                 a = 75
let x-d = 35
      x = 36 
     x+d = 37
adding them we get 
  3x = 429 
 a19 = a+(n-1)d
 75 = a+18d
a36= a+35d
143 = a+35d
from both the equations we get 
a = 3
and d = 4
so the AP is 3 , 7 , 11 ...