An important question from arithmetic progression chapter as it was already asked in previous year paper of 2013 in which we have been asked to prove that 72nd term is 4 times its 15th term, if the 24th term of an AP is twice its 10th term.
Book – RS Aggarwal, class 10, chapter 5A, question no 38
Let a=Â first term of A.P.,
d=Â common difference
nth term, a24​=2a10​
⇒a+23d=2(a+9d)
⇒a+23d=2a+18d
⇒a=5d
Now,
​a72/a15​​=(a+71d)​/(a+14d)
       =76d​/19d
       =4.