Question

20cm long cylinderical pencils of diameter 1cm each are packed in a cuboidal box in two rows . If there are 20 pencils to be arranged in this box, then what is the surface area of this box?

Answer 1

Dimensions of the cyliderical pencil is,

Diameter = d = 1 cm

Length of the pencil = 20 cm

Given 20 pencils are arranged in a cubiodal box

in two rows,

Now dimensions of the cuboidal box is

Lenth = l = each pencil length = 20 cm

breadth = b = 10 × each pencil diameter = 10 × 1cm = 10cm

Height = h = 2 × each pencil diameter = 2 × 1 cm = 2 cm

Total surface area of the box = 2 ( lb + bh + lh )

= 2 ( 20 × 10 + 10 × 2 + 20 × 2 )

= 2 ( 200 + 20 + 40 )

= 2 × 260

= 520 square cm.

Answer 2

the pencil are 20 cm long which means the lenght of the box= 20cm

as given

they are arranged in two rows and there are 20 pnecil so

pencil in one row=20/2=10pencil

if one pencil have a diameter of 1cm then,

daimeter of 10 pencils= breath of the box

1×10= 10 cm

the breath of the box is 10cm

now,

the height of the box will be equal to sum of the daimeter of 2 pencil as they are arranged in a parallel way

h of box = 2cm

LSA of cuboid=2(LB)h

=2(10•20)2

=120cm^2
TSA OF CUBOID=2(LB+BH+HL)
2(20•10+10•2+20•2)
520sqcm