Question

"Question 7 Shanti Sweets Stall was placing an order for making cardboard boxes for packing their sweets. Two sizes of boxes were required. The bigger of dimensions 25 cm × 20 cm × 5 cm and the smaller of dimensions 15 cm × 12 cm × 5 cm. For all the overlaps, 5% of the total surface area is required extra. If the cost of the cardboard is Rs 4 for 1000 cm^2 , find the cost of cardboard required for supplying 250 boxes of each kind.

Class 9 - Math - Surface Areas and Volumes Page 213"

Answer 1

Dimension of bigger box = 25 cm × 20 cm × 5 cm

Total surface area of bigger box = 2(lb + bh + lh)
   = 2(25×20 + 20×5 + 25×5)
  = 1450cm2

Dimension of smaller box = 15 cm × 12 cm × 5 cm

Total surface area of smaller box = 2(lb + bh + lh)
= 2(15×12 + 12×5 + 15×5)
= 630cm2

Total surface area of 250 boxes of each type = 250(1450 + 630)                                             =250×2080 cm2 = 520000 cm2
Extra area required = 5/100(1450 + 630) × 250 cm2 = 26000 cm2

Total Cardboard required = 520000 + 26000 cm2 = 546000 cm2

Total cost of cardboard sheet = ₹(546000 × 4)/1000 = ₹ 2184

Answer 2

Hi friend ...
In the case of bigger box.

TSA=2(lb+bh+hl)

=2(25×20×20×5+5×25)cm square.

=2(500+100+125)cm square

=1450cm square


In the case of smaller box:-
l=15cm
B=12cm
and height 5cm


TSA=2(lb+bh+hl)

=2(15×12+12×5+5×15)cm square

=2(180+60+79)cm square

=(2×315)cm square

=630cm square

Total surface area of 250 boxes of each type

=250(1450+630)cm square

=(250×2080)cm square

=520000cm square

Cardboard required

=(520000×105/100)cm square

=546000 cm square

Cost of 1000 cm square of cardboard.

=₹4

So that, total cost of cardboard

=₹(546000/1000×4)

=Rs 2184.


Hope it helps ⛎⛎⛎⛎✋