What is the value of 21 + 24 + 27 + ...... + 51?A360B380C374D396Answer: D. 396 Read Explanation: Nth term=a + (n - 1)d N is 51 and d = 3, 51 = 21 + (n - 1) × 3 ⇒ n = 11 Sum of n terms of an AP = n/2(2a + (n - 1)d) sum=396Read more in App