Posted by acshikari on Friday, July 29, 2011 at 9:38pm.
The volume of the box is 900 cubic inches. Find the dimension with a ratio of 1:3:5.

solid mensuration  Damon, Friday, July 29, 2011 at 9:44pm
1x * 3x * 5x = 900
15 x^3 = 900
x^3 = 60
x = 3.915
3x = 11.745
5x = 19.574 
solid mensuration  Reiny, Friday, July 29, 2011 at 9:45pm
let the dimensions be x , 3x, and 5x
x(3x)(5x) = 900
15x^3 = 900
x^3 = 60
x = ∛60
dimensions are ∛60 , 3∛60, and 5∛60
or appr. 3.91 , 11.74, and 19.57
check: 3.91*11.74*19.57 = 898.33 close for the approximation I used
however, ∛60*3∛60*5∛60 = exactly 900 
solid mensuration  acshikari, Friday, July 29, 2011 at 10:03pm
wow!!!
thnk you so much damon and reiny for helping
now i knw how to use ratios. tnx a lot:)