In an Arithmetic Progression, T7 = 18 and T18 = 7, obtain T25.

Here T7 = 18
T18 = 7
d = (Tm - Tn) / (m - n)
d = (T18 - T7) / (18 - 7) = 7 - 18 / 11 = -1
Now, T7 = 18 => a + 6d = 18 => a + 6(-1) = 18 => a = 24
Now, T25 = a + 24d = 24 - 24 = 0
Thus, T25 = 0