Example 11 - Find sum of first 22 terms of AP: 8, 3, -2, .. - Finding sum of n terms

  1. Chapter 5 Class 10 Arithmetic Progressions
  2. Serial order wise
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Example 11 Find the sum of the first 22 terms of the AP : 8, 3, 2, . . . 8,3, 2, We have to find sum of first 22 terms . Sum = /2 (2a + (n 1) d) Here n = 22, a = 8 d = 3 8 = 5 Putting there values in formula, Sum = /2 [2 +( 1) ] = 22/2[2 8+(22 1)( 5)] = 11[16+(21)( 5)] = 11[16 105] = 11[ 89] = 979

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