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 cm, find the total expenses required for polishing and painting the surface of the bookshelf?
Answers
Answer:
External length (l) of bookshelf=85㎝
External breadth (b) of bookshelf=25㎝
External height (h) of bookshelf=110㎝
External surface area of book shelf while leaving out the front face of the shelf=lh+2(lb+bh)
=(85×110)+2(85×25+25×110)
=9350+9750
=19100㎠
Area if front face=(85×110)−75×100+2(75×5)
=1850+760=2600㎠
Area to be polished=19100+2600=21700㎠
Cost of polishing=Rs. 21700×0.20=Rs.4340
Length, breadth and height of each row of bookshelf are
75㎝,20㎝ & 30㎝ respectively. From the figure Area to be painted in 1 row=2(l+h)b+lh
=2(75+30)20+75×30
=6450㎠
Area to be painted in 3 rows=3×6450=19350㎠
Total cost of painting=Rs.(19350×0.1)=Rs. 1935
Total expenses=Rs.(4340+1935)=Rs. 6275
Answer:
External length (l) of bookshelf=85㎝
External breadth (b) of bookshelf=25㎝
External height (h) of bookshelf=110㎝
External surface area of book shelf while leaving out the front face of the shelf=lh+2(lb+bh)
=(85×110)+2(85×25+25×110)
=9350+9750
=19100㎠
Area if front face=(85×110)−75×100+2(75×5)
=1850+760=2600㎠
Area to be polished=19100+2600=21700㎠
Cost of polishing=Rs. 21700×0.20=Rs.4340
Length, breadth and height of each row of bookshelf are
75㎝,20㎝ & 30㎝ respectively. From the figure Area to be painted in 1 row=2(l+h)b+lh
=2(75+30)20+75×30
=6450㎠
Area to be painted in 3 rows=3×6450=19350㎠
Total cost of painting=Rs.(19350×0.1)=Rs. 1935
Total expenses=Rs.(4340+1935)=Rs. 6275