Here,
Volume of 1 small cube = \(5^3 = 125\)

Total volume of all 3 cubes = \(3 * 125 = 375\)

Now, let check with each option

a) 6.9 : Volume of the cube = \((6.9)^3 = 328\). This is not possible since the volume of larger cube aquarium < 3 small cube aquarium

b) 8.4 : Volume of the cube = \((8.4)^3 = 592\). Now 50% of 592 = 296 = This is one possible solution, since 375 (smaller cube aquarium) > 50% of Larger aquarium

c) 9.5 : Volume of the cube = \((9.5)^3 = 857\). Now 50% of 857 = 428 = This is not possible as the volume of smaller cubes = 375 and is < 50% volume of larger aquarium

Option B
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Isn't this a 3D shape problem ? It will be helpful if the tag is corrected
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