The sum of the fourth and twelfth term of an arithmetic progression is 20. What is the sum of the first 20 terms of the arithmetic progression?
Choose the correct choice:  A) 300  B) 120  C) 150  D) 170  E) 200
n th term of A.P. is given by a+(n-1)d   4 th term = a+3d   12 th term = a+11d   Given a+3d+a+11d=20 --&gt; 2a+14d=20 --&gt; a+7d = 10   Sum of n term of A.P = n/2[2a+(n-1)d]   subsitiuing n = 20 ...we get 20/2[ 2a + 14d] = 20 [a+7d] = 20*10 = 200...   Answer is 200...
<result>E</result>
The sum of the fourth and twelfth term of an arithmetic progression is 20. What is the sum of the first 20 terms of the arithmetic progression?