Question

How much glass (in cm ${}^2$) will be required to contstruct a kaliedoscope of length $20$ cm having an equilateral triangle of side $8$ cm as the base?

• A. $348$ cm${}^2$
• B. $580$ cm${}^2$
• C. $480$ cm${}^2$

Answer 1

The correct option is C $480$ cm${}^2$


The glass will be used in the $3$ rectangular sides of the triangluar prism, which means they will cover the lateral surface area of the prism.

The length and breadth of the rectangular sides are $20$ cm and $8$ cm respectively.
$\therefore$ Lateral surface area $=3\times$ area of $1$ rectangular side $=3\times (20\times 8)$
$=3\times 160=480$ cm${}^2$

Option (c.) is correct.