Question

maria wants to make an open cuboidal box 10cm long 5cm wide and 3cm high from a cardbord find the cost of the cardboard at the rate of 50 paisa per cm

Answer 1

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 !

Answer 2

find the total surface area and then subtract area (lb) of the cupboard and then multiply by 50 paise.
for converting into rupees divide by 100.