Question

A small indoor greenhouse (herbarium) is made entirely of glass panes (including base) held together with tape. It is $30cm$ long, $25cm$ wide and $25cm$ high.
(i) What is the area of glass?
(ii) How much of the tape is needed for all of the $12$edges?

Answer 1

Hint- Total surface area of the room is given as $2(lb + bh + hl)$ and total length of edges is equal to $4(l + b + h)$. Use the formulas to calculate the answer.

Area of the glass is equal to the total surface area of the room.
Given that:
$length = 30cm,breadth = 25cm,height = 25cm$
Total surface area = $2(lb + bh + hl)$
$
   = 2((30 \times 25) + (25 \times 25) + (25 \times 30)) \\
   = 2(750 + 625 + 750) \\
   = 4250c{m^2} \\
$
Area of the glass is $4250c{m^2}$
Now, we need to calculate the total length of edges which is given by
$
   = 4(l + b + h) \\
   = 4(30 + 25 + 25) \\
   = 320cm \\
$
Hence a tape of length $320cm$ is required.

Note- These types of problems are mainly based on formulas of area. To solve the types of problems, you should be familiar with the formulas of the area of cuboids, cube, triangle, square and trapezium.