If the sum of the 4th term and the 12th term of an arithmetic progression is 30, what is the sum of the first 15 terms of the progression?
Select the correct option:
A) 250
B) 275
C) 260
D) 225
E) 230
4th term + 12th term = 30   i.e., (a+3d)+(a+11d) = 30   Now, Sum of first 15 terms = (15/2) * [2a + (15-1)d]   = (15/2) * [2a + 14d]   = (15/2) * 30 --------------- From (1)   =225   Answer : 225
<result>D</result>
If the sum of the 4th term and the 12th term of an arithmetic progression is 30, what is the sum of the first 15 terms of the progression?