If the sum of the 4th term and the 12th term of an arithmetic progression is 12, what is the sum of the first 15 terms of the progression? Choose the correct option
A) 90	B) 80	C) 70	D) 60	E) 50
4th term   + 12= 
<gadget id="calculator">  + 12</gadget>
<output>12</output>
12   i.e., (a+3d)+(a+11d)= 12   Now, Sum of first 15 terms = (15/2) * [2a + (15-1)d]   = (15/2) * [2a + 14d]   = (15/2) * 12 --------------- From (1)   =90   90nswer : 90
<result>A</result>
If the sum of the 4th term and the 12th term of an arithmetic progression is 12, what is the sum of the first 15 terms of the progression?