Question

014.
A wooden shelf has external dimensions as longth
100 cm depth 40 cm and breadth 90 cm. The
thickness of plank is 10 cm overywhere. Al external
faces are to be polished and the inner faces are to
bo painted. If the rate of polishing is 0.50 par
oma and the rate or painting is + 2 per cm.
then find the total expenses required for polishing
and painting the surtaces of book shelf
TE
100 cm
T
40 cm
90 cm​

Answer 1

Step-by-step explanation:

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

Just change the values :)