The Total solution for NCERT class 6-12
In the A.P. 63, 65,67, …a = 63 and d = 65 – 63 = 2an = a1 + (n – 1) d = 63 + (n – 1) x 2 = 63 +2n – 2 = 61 + 2nand in the A.P. 3, 10, 17, …a = 3 and d = 10 – 3 = 7an = a + (n – 1) d = 3 + (n – 1) x 7 = 3 + 7n – 7 = 7n – 4But both nth terms are equal61 + 2n = 7n – 4=> 61 + 4 = 7n – 2n=> 65 = 5n=> n = 13n = 13