Box made of material of uniform thickness: internal vs external dimensions

This type of question, asked 2 times: CDS 2 2022, CDS 1 2025. All 2 questions below, oldest first.

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Question 1
CDS 2 2022
91 $A closed box is built of wood of uniform thickness. Its external dimensions are 12 cm, 10 cm and 8 cm. If the inner surface area is 376 square cm, then what is the thickness of the wood ?$
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Question 2 (case study, 2 parts)
CDS 1 2025
The sides of an open box are 0.5 cm thick and bottom is 1 cm thick. The internal length, breadth and depth are respectively 14 cm, 10 cm and 8 cm. It is completely filled with water.
63 $If the material weighs 2000 kg per cubic metre, then what is the weight of the material used in the construction of the box ?$
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64 $If water weighs 1000 kg per cubic metre, then what is the weight of the box with water ?$
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Question 1