Let AA' = a, AB = b, AD = d
Volume of the parallelopiped T,
V = a.(b × c)
Let AA'' = r
Let V1, the volume of the new box = r.(b × c)
It is given that V1 = (90/100)V2 = (9/10)V2.
Thus, V1 = (r – 0.9a).(b × c)
r lies on a plane passing through 0.9a, and perpendicular to (b × c).