Question

A plastic box $1.5$ m long, $1.25$ m wide and $65$ cm deep is to be made. It is opened at the top. Ignoring the thickness of the plastic sheet,
(i) determine the area of the sheet
(ii) the cost of sheet for it, if a sheet measuring $1$ m${}^2$ costs Rs.$20$.

Answer 1

Given:

Length of box $=1.5$ m, Breadth $=1.25$ m, Height $=0.65$ m

$\Rightarrow$Area to be white-washed $=$ Area of cuboid $-$ Area of base.

(i) Area of sheet requred $=2lb+2bh+2lh-lb$

(i) Area of sheet requred $=2lh+2bh+lb$ .....[Box is open]

$=[2\times 1.5\times 0.65+2\times 1.25\times 0.65+1.5\times 1.25]$ m${}^2$

$=(1.95+1.625+1.875)m^2=5.45$ m${}^2$

ii) Cost of sheet per $m^2$ area $=$ Rs. $20$

Cost of sheet of $5.45m^2$ area $=$ Rs. $5.45\times 20$
$=$ Rs. $109$