Length (l1) of bigger box = 25 cm
Breadth (b1) of bigger box = 20 cm
Height (h1) of bigger box = 5 cm
Total surface area of bigger box = 2(lb + lh + bh)
= [2(25 × 20 + 25 × 5 + 20 × 5)] cm2
= [2(500 + 125 + 100)] cm2
= 1450 cm2
Extra area required for overlapping
= (1450 x 5/100) cm2 = 72.5 cm2
While considering all overlaps, total surface area of 1 bigger box = (1450 + 72.5) cm2 =1522.5 cm2
Area of cardboard sheet required for 250 such bigger boxes = (1522.5 × 250) cm2 = 380625 cm2
Similarly, total surface area of smaller box = [2(15 ×12 + 15 × 5 + 12 × 5] cm2
= [2(180 + 75 + 60)] cm2
= (2 × 315) cm2
= 630 cm2
Therefore, extra area required for overlapping = (630 x 5/100) cm2
= 31.5 cm2
Total surface area of 1 smaller box while considering all overlaps
= (630 + 31.5) cm2 = 661.5 cm2
Area of cardboard sheet required for 250 smaller boxes = (250 × 661.5) cm2 = 165375 cm2
Total cardboard sheet required = (380625 + 165375) cm2 = 546000 cm2
Cost of 1000 cm2 cardboard sheet = Rs 4
Cost of 546000 cm2 cardboard sheet
= Rs(546000 x 4/1000) = Rs 2184
Therefore, the cost of cardboard sheet required for 250 such boxes of each kind will be Rs 2184.