Arithmetic and Geometric Progressions

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Arithmetic Progression

    Second term in an AP is 8 and the 8th term is 2 more than thrice the second term. Find the sum up to 8 terms of this AP.
    1. 124
    2. 108
    3. 96
    4. 110

 

  • Correct Answer
    Choice A. 124

Detailed Solution

Given, Second term of an AP is 8 => a+d =8, 8th term is 2 more than thrice the second term => a+7d = 2 +3(a+d) = 2+3*8 =26 .

a+d =8 -------------- 1

a+7d = 26 -------------- 2

Solving for d in the two equations, we get d = 3 and a =5. Sum of n terms in an AP = * [2a +(n-1)d].

=> Sum upto 8 terms in this AP = * [2*5 + (8-1)3] => 4*[10+21] = 4*31 = 124.

Correct Answer: 124



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More questions from Progressions

  1. Counting and Progressions
  2. Common Ratio
  3. Common Difference
  4. Sum up to 'n' Terms
  5. AP Puzzle
  6. GP Logical Puzzle
With some simple but very powerful ideas, one can cut down on a lot of working when it comes to progressions. For example, anchoring a progression around its middle term can be very useful. Reinforce these ideas with these questions.