A basic question from arithmetic progression chapter as it is already asked in previous year paper of 2009 in which we are to find the middle term of the AP 10, 7, 4,…..,(-62).
RS Aggarwal, class 10, Arithmetic Progression, chapter 5A, question no 18.
Given series is 10,7,4,−−−−−(−62)
first term (a)=10
d=7−10
=−3
therefore,
−62=10+(n−1)(−3)
−3(n−1)=−62−10
−3(n−1)=−72
n−1=−72/-3
n−1=24
n=24+1=25
therefore,
mid-terms is (25+1)/2
=26/2=13
13th terms=10+(13−1)×(−3)
=10−36
=−26