Find the sum of first 40 terms of an ap whose 4 th term is 8 and 6th term is 24

1 thought on “Find the sum of first 40 terms of an ap whose 4 th term is 8 and 6th term is 24”

1. ANSWER

   S40=5800

   Step-by-step explanation:

   A4=A+3d=8 …(1)

   A6=A+5d=24 …(2)

   (1)–(2)

   A+3d=8

   –A–5d=–24

   _________

   –2d=–16

   d=8

   A+3(8)=8

   A=–16

   S40=n/2(2a+(n–1)d)

   S40=20(–32+(39)8)

   S40=20(–32+312)

   S40=20(290)

   S40=5800

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