In an APGiven a12 = 37, d = 3, find ‘a’ and S12. from Math

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 Multiple Choice QuestionsShort Answer Type

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65.

In an AP
Given a12 = 37, d = 3, find ‘a’ and S12.


Here,    a12 = 37,   d= 3
We know that,
      a= a + (n - 1)d
rightwards double arrow a12 = a + (12 - 1) x 3
rightwards double arrow 37 = a + 11 x 3
rightwards double arrow
 a = 37 - 33 = 4
And,     straight S subscript straight n space equals straight n over 2 straight x space left parenthesis straight a plus straight l right parenthesis
therefore space space space straight S subscript 12 equals 12 over 2 straight x space left parenthesis 4 plus 37 right parenthesis
space space space space space space equals space 6 straight x space 41 space equals space 246
Hence comma space space space straight a space equals space 4
and space straight S subscript 12 space equals space 246 end subscript 

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