The Total solution for NCERT class 6-12
We know that,Tn = a + (n – 1 )dT5 = a + 4d => a + 4d = 31 ……(i)and T25 = a + 24d=>a + 24d = 140 + T5=> a + 24d = 140 + 31 = 171 …..(ii)Subtracting (i) from (ii),20d= 140and a + 4d = 31=> a + 4 x 7 = 31=> a + 28 = 31=> a = 31 – 28 = 3a = 3 and d = 7AP will be 3, 10, 17, 24, 31, ……..