Question

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 $c{m}^2$ and the rate of painting is 10 paise per $c{m}^2$ find the total expenses required for polishing and painting the surface of the bookshelf.

Answer 1

It can be observed that length (I), breadth (b), and height (h) of each row of the book shelf is 75 cm, 20 cm, and 30 cm respectively.
Area to be painted in 1 row = 2(I + h) b + Ih
$=\left[2\right(75+30)\times 20+75\times 30]c{m}^2=(4200+2250)c{m}^2=6450c{m}^2$
Area to be painted in 3 rows $=(3\times 6450)c{m}^2=19350c{m}^2$
Cost of painting 1 $c{m}^2$ area = Rs 0.10
Cost of painting 19350 $c{m}^{2}area=Rs(19350\times 0.1)=Rs1935$
Total expense required for polishing and painting = Rs (4340 + 1935)
= Rs 6275
Therefore, it will cost Rs 6275 for polishing and painting the surface of the bookshelf.