Question

An ap consist of 37 terms. The sum of the three middle most term i 225 and the sum of the last three term is 429.Find the Ap

Answer 1

May this will help you

Answer 2

n = 37
37/2 = 18.5
so a17 + a 18 + a19 = 225
a + 16d + a + 17d + a + 18d = 225
3a + 51d = 225
a + 17d = 75 .... I)

a35 + a36 + a37 = 429
a + 34d + a + 35d + a + 36d = 429
3a + 105d = 429
a + 35d = 143 ... ii)
frm eq I, a = 75 - 17d

substituting value of a in ii)
75 - 17d + 35d = 143
18d = 143 - 75
d = 68/18
d = 34/9
a = 75 - 17d
a = 75 - 17 × 34/9
a = 75 - 578/9

675 - 578
a = -----------------
9
a = 97 /9