An important and exam oriented question from arithmetic progression chapter as it was already asked in previous year paper of 2015 in which we have been asked to find its common difference, if the 4th term of an AP is 11. The sum of the 5th and 7th term of this AP is 34.
RS Aggarwal, Class 10, Arithmetic Progression, chapter 5A, question no 29.
T4=11
T5+T7=34
a+3d=11,
a+4d+a+6d=34
2a+10d=34
a+5d=17
⇒(a+5d)−(a+3d)=17−11
⇒2d=6
⇒d=3.