Open-top cuboid from a 7 cm square sheet with corner squares of area 0.25 cm^2 removed:\nFind the volume (in cubic centimetres) of the resulting open-top box after folding.

Introduction / Context:
Cutting equal squares from each corner of a sheet and folding up the flaps creates an open-top cuboid. Its height equals the side of the removed square; base dimensions shrink by twice that amount.

Given Data / Assumptions:

• Square sheet: side 7 cm.
• Each cut-out square has area 0.25 cm^2 → side = √0.25 = 0.5 cm.

Concept / Approach:
Final box: length = 7 − 2*0.5 = 6 cm; breadth = 7 − 2*0.5 = 6 cm; height = 0.5 cm. Volume = l * b * h.

Step-by-Step Solution:

Verification / Alternative check:
Unit consistency: base area 36 cm^2 times height 0.5 cm gives 18 cm^3.

Why Other Options Are Wrong:
21, 16, 20, 24 do not match 6*6*0.5.

Common Pitfalls:
Using the area 0.25 as the side directly, or forgetting to subtract twice the cut size from each dimension.

Final Answer:
18