In an AP, p, q and r are positive integers such that \(q-p=r-q\). Which relation among these terms is always true?
Answer and explanation
Correct answer: \(a_p+a_r=2a_q\)
For an AP, \(a_k=a_1+(k-1)d\). As \(q-p=r-q\), we get \(p+r=2q\), so \(a_p+a_r=2a_q\). The product relation is associated with a GP, not an AP. Exam tip: equally spaced indices make the middle term the average.
Frequently asked questions
What is the correct answer to this question?
\(a_p+a_r=2a_q\)
Why is this the correct answer?
For an AP, \(a_k=a_1+(k-1)d\). As \(q-p=r-q\), we get \(p+r=2q\), so \(a_p+a_r=2a_q\). The product relation is associated with a GP, not an AP. Exam tip: equally spaced indices make the middle term the average.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Arithmetic Progressions (AP). Topic: Finding the $n$th term of an AP.