Question

1. A wooden bookshelf has external dimensions as
follows: Height = 110 cm, Depth = 25 cm,
Breadth = 85 cm (see Fig. 13.31). The thickness of
the plank is 5 cm everywhere. The external faces
are to be polished and the inner faces are to be
painted. If the rate of polishing is 20 paise per
cm' and the rate of painting is 10 paise per cm²,
find the total expenses required for polishing and
painting the surface of the bookshelf.
pls tell fast​

Answer 1

Answer:

Step-by-step explanation:

External length =85cm

External breadth =25cm

External height =110cm

External SA=lh+2(lb)+2bh

=85×110+2(85×25+25×110)

=(9350+9750)cm

2

=19100cm

2

Area to be polished =19100+2600=21700cm

2

Cost of polishing 1cm

2

 area 0.20Rs

Cost of polishing 21700cm

2

 area =21700×0.20

=Rs. 4340

Now, area to be painted in 3 rows =3× area to be painted in 1 row

=3×[2(l+b)b+lh]

=3[2(75+30)×20+30×75]

=3[4200+2250]=19350cm

2

Cost of painting 1 cm

2

 area =0.10Rs

Cost of painting 19350 area =Rs.1935

Total cost =1935+4340

=Rs.6275