The distance  travelled by a body in last second  of upward journey is D. If the velocity of projection is halved then the distance travelled in last second of upward journey is

Distance covered in nth second= Sn=U+gn−12  here initial velocity=U;acceleration due to gravity=g 'n′ is last second, n=Ug⇒D=U−gUg−12⇒D=U−U+g2⇒D=g2---(1)case2   initial velocity=U2; lastsecond=U2g Sn=U+gn−12Sn=U2-gU2g−12Sn=g2substitute equation(1)Sn=D