A particle moving with a constant acceleration describes in the last second of its motion 925th of the whole distance. If it starts from rest, how long is the particle is motion.

Given  u=0 sn=925sFrom equation  sn=u+an−12⇒925s=an−12............(1)∴ But the total distance travelled in ‘n’ sec iss=u(n)+12a(n)2=0+12a(n)2……...(2) From (1) and (2) ∴92512an2=a(2n−1)2⇒925=2n−1n2⇒n=5sec