Question

Find the number of square stamps each of side 2 in x 2 in as shown required to cover the whole box leaving the triangular face?

• A. 12
• B. 18
• C. 24
• D. 36

Answer 1

The correct option is C 24

To find out the number of stamps required to cover the box, we will divide the area of the surface of box excluding the triangular faces by the area of the each stamp.

$\text{Area of each stamp =}2\times 2$
$=4sqin$

Area of triangular prism excluding the triangular faces is the area of its 3 lateral rectangle faces.

$\text{Area of lateral faces =}8\times 5+8\times 3+8\times 4$
= 40 + 24 + 32
= 96 sq in

$\text{Number of stamps pasted =}\frac{\text{Area of the surface}}{\text{Area of stamp}}$

$=\frac{96}{4}$
$=24$
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∴ Number of stamp that can be pasted to cover the box are 24.