Volume of a cuboid = Length × Breadth × Depth Calculation: Let the length of the tank be ' L '. Then, depth =L∕2 And, breadth =1∕4×(L−L∕2)=1∕4×(L∕2)=L∕8 Now, we use the volume formula: Volume =L×(L∕8)×(L∕2) 256=(L3)∕16 ⇒L3=256×16 ⇒L3=4096 ⇒L=3√4096 ⇒L=16cm