What is the sum of the first 15 terms of an A.P whose 11 th and 7 th terms are 5.25 and 3.25 respectively Choose the most appropriate option: A) 56.25 B) 60 C) 52.5 D) 5.25 E) None of these
a +10d = 5.25, a+6d = 3.25, 4d = 2, d = ½   a +5 = 5.25, a = 0.25 = ¼, s 15 = 15/2 ( 2 * ¼ + 14 * ½ )   = 15/2 (1/2 +14/2 ) = 15/2 *15/2 =225/ 4= 
<gadget id="calculator">225/ 4</gadget>
<output>225/4 = around 56.25</output>
56.25   56.25NSWER:56.25
<result>A</result>
What is the sum of the first 15 terms of an A.P whose 11 th and 7 th terms are 5.25 and 3.25 respectively