An important question from Arithmetic progression chapter as it was already asked in previous year paper of 2005 in which 4ht term is 0 and we have to prove that it’s 25th term is triple it’s 11th term.
RS Aggarwal, Class 10, Arithmetic Progression, chapter 5A, question no 27
Let first term of an A.P=a
common difference of A.P=d
According to question,
a+3d=0…….(1)
25th term =a+24d
from (1)…a=−3d
=> −3d+24d
=> 21d…..(2)
11th term=a+10d
=−3d+10d
=7d…..(3)
By (3) and(2) 25th term=3× 11th term
Hence proved