Question

A wooden bookshelf has external dimensions as follows: Height = 110 cm, Depth = 25 cm, Breadth = 85 cm (See Figure). The thickness of the plank is 5 cm every where. 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.

Answer 1

External dimensions of the bookshelf are,

Length,

Breadth,

Height,

External surface area of the bookshelf excluding the front face,

Area of the front face,

Area to be polished,

Rate of polishing

Total cost of polishing,

Now, above diagram will make it clear that for each row of bookshelf,

Length

Breadth

Height

Hence, area to be painted in one row,

Area to be painted in three rows,

Rate of painting

Total cost of painting,

Total Expense

Therefore, the total expenses are.