The numbers between 200 and 400 which are divisible by 7 are 203, 210, 217,......, 399. This sequence forms an A.P., whose first term is 203 and difference is 7. Let 399 be the nth term of sequence, then 399 = 203 + (n – 1) 7 ⇒ (n – 1) 7 = 399 – 203 ⇒ (n – 1)7 = 196 ⇒ n – 1 = 28 ⇒ n = 29 Hence, total number of terms in A.P. are 29. ∴ Sum of 29 terms = $\frac{29}{2}$ [2 (203) + (29 - 1) 7] i.e., $S_{29}$ [406 + 196] = $\frac{29}{2}$ × 602 = 8729