1.

First term and common difference of an A.P are 6 and 3 respectively find s 27​

Answer»

S O L U T I O N :

GIVEN,

  • First term (a) = 6
  • Common difference (d) = 3

To Find,

  • SUM of 27 terms.

Explanation,

We know that,

Sum of nth terms,

=> Sn = n/2 × (2a + (n - 1)d)

[ Here, n = 27 ]

=> S_27 = 27/2 × (2 × 6 + (27 - 1) × 3)

=> S_27 = 27/2 × (12 + 26 × 3)

=> S_27 = 27/2 × (12 + 78)

=> S_27 = 27/2 × (90)

=> S_27 = 27 × 45

=> S_27 = 1215

Therefore,

The sum of 27 terms is 1215.


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