Question

maria wants to make an open cuboidal box 10 cm long,5 cm wide and 3 cm high from a cardboard.Find the cost of the cardboard at the rate of 50 paisa cm sq.

Answer 1

formula of rhombus area

Answer 2

In order to find the cost of cardboard, we need to first find the area of cardboard and then multiply it to the cost.
So, the surface are of an open cuboidal box = Total surface area - area of the top
= 2(lb + bh + hl) - lb
= 2(bh + hl) - lb
= 2(5x3 + 3x10) - 10x5
= 2 x 45 - 50 
= 90 - 50
= 40 cm²
Therefore, the cost of the cardboard = 40 x 50
= 200 paisa
= Rs 2

Hope it helps !!