Length of room, l = 5 m
breadth, b = 4m
height, h = 3 m
White washing the room and the ceiling except floor to be made.
∴ Area, A = lb + 2bh + 21h
= lb + 2h(b + l) = (5 × 4) + 2 × 3(4 + 5)
= 20 + 6(9)
= 20 + 54 = 74 m2 .
Cost of white washing for 1 sq.m. is Rs. 7.50
∴ Cost of white washing 74 sq. m. is ?
= 74 × 7.50
= Rs. 555.