A closed aquarium of dimensions 30 cm × 25 cm × 20 cm is made up entirely of glass plates held together with tapes. The total length of tape required to hold the plates together (ignore the overlapping tapes) is (Hotel Management, 2009)

### Concept & Total Length of Edges The tape is used along the joints of the glass plates. Since it's a cuboidal aquarium, the joints correspond exactly to the edges of the cuboid. $$\text{Total Edge Length} = 4(l + b + h)$$ ### Step-by-Step Solution * **Given:** Length ($l$) = $30\text{ cm}$, Breadth ($b$) = $25\text{ cm}$, Height ($h$) = $20\text{ cm}$. * A cuboid has 12 edges in total: 4 lengths, 4 breadths, and 4 heights. * **Step 1: Sum the dimensions** Sum = $l + b + h = 30 + 25 + 20 = 75\text{ cm}$. * **Step 2: Multiply by 4** Total Tape Length = $4 \times 75\text{ cm} = 300\text{ cm}$. ### Exam Strategy & Shortcut Recognize that "length of tape" means "perimeter of all faces combined but counted without overlap", which is just the sum of all edges. Add the three given numbers ($30+25+20 = 75$) and multiply by $4$. ### Common Pitfall Many students calculate the surface area or volume by mistake, or they only sum $l + b + h$ once (Option A) or multiply by 2 (Option C) instead of 4. ### Final Answer Therefore, the correct answer is **300 cm**.