# CAT Quantitative Aptitude Questions | CAT Algebra - Progressions questions

###### CAT Questions | Algebra | Arithmetic Progressions - Sum of N terms
CAT Questions

The question is about sum of N terms of an Arithmetic Progression. If modulus of two terms in an AP is equal, how we can determine whether the series is increasing or decreasing? For that we need more details. 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. CAT Exam tests the idea of progression often in the CAT Quantitative Aptitude section and this could also be tested in DI LR section of the CAT Exam as a part of a puzzle.

Question 4: Let the nth term of AP be defined as tn, and sum up to 'n' terms be defined as Sn. If |t8| = |t16| and t3 is not equal to t7, what is S23?

1. 23(t16 - t8)
2. 0
3. 23t11
4. Cannot be determined