Answer:
x= 3 inch should be turned up on each side
Step-by-step explanation:
Let the height of trough be x.
Width of trough be 12 - 2x.
and length of trough = 120 inch
Volume of trough, V = L×W×H = 120 × (12-2x) × x = 120x(12 - 2x)
For maximum volume, we find V' = 0
i.e 1440 -480x = 0
or x =
or x= 3
Hence x= 3 inch should be turned up on each side