Question

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

Answer 1

Length of open wood box (L) = 1. 48 m = 148 cm

$Breadth\left(B\right)=1.16m=116cm$

$andheight\left(H\right)=8.3dm=83cm$

$\text{Thickness of wood}=3cm$

$\therefore \text{Inner length}\left(l\right)=148-2\times 3$$=148-6=142cm$

$Breadth\left(b\right)=116-2\times 3$$=116-6=110cm$

$\text{and~height~(h)}=83-3=80cm$

$\therefore \text{Surface area of inner of box}$$=2h(l+b)+l\times b$

$=2\times 80[142+110]+142\times 110c{m}^2$

$=160\left[252\right]+142\times 110c{m}^2$

$=160\times 252+142\times 110c{m}^2$

$=40320+15620c{m}^2$

$=55940c{m}^2=\frac{55940}{100\times 100}{m}^2=5.594m^2$

$Rateofpainting=Rs50per{m}^2$

$\therefore \text{Total cost}=Rs50\times 5.594$$=Rs279.70$