85 cm
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
cm² and the rate of painting is 10 paise per cm²,
find the total expenses required for polishing and
painting the surface of the bookshelf.
Answers
Answer:
6275
Step-by-step explanation:
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
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(4340+1935)=Rs.6275
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