Answer: 5.24 units, 10.48 units , 15.72 units
Step-by-step explanation:
Volume of a rectangular solid is given by :-
V = lwh, where l = length , w= width and h = height
Given: A rectangular solid has edges whose lengths are in the ratio 1:2:3.
Let lengths of the rectangular solid x , 2 x, 3x.
volume of the solid is 864 cubic units
Then, Volume of rectangle = 

Lengths of rectangular solid 5.24 units, 2 (5.24) units , 3(5.24) units
= 5.24 units, 10.48 units , 15.72 units