Question

An open box is made of wood $3cm$ thick. Its external length, breadth and height are $1.48m,1.16m$ and $8.3dm$. Find the cost of painting the inner surface at $Rs.50persq.$ metre.

• A. $Rs.279.70$
• B. $Rs.270.10$
• C. $Rs.219.70$
• D. $Rs.179.70$

Answer 1

The correct option is A $Rs.279.70$

Thickness of wood$=3cm$
length of open box$=1.48m=148cm$
breadth of open box$=1.16m=116cm$
height of open box$=8.3dm=83cm$
inner length,$l=148-(2\times 3)=142cm$
inner breadth,$b=116-(2\times 3)=110cm$
inner height, $h=83-3=80cm,$ box is open.
area of inner surface$=2(lb+bh+hl)-lb=2(142\times 110+110\times 80+80\times 142)-[142\times 110]=2(15620+8800+11360)\left(15620\right)=71563--15620=55940{cm}^2=50594m^2$
cost of painting inner surface$=5.594\times 50=Rs.279.70$