Question

7. Two cubes each of edge 12 cm are joined. The surface area of new cuboid is
(a) 140 cm (b) 1440 cm? (c) 144 cm
(d) 72 cm?​

Answer 1

Answer:

1440 cm

Step-by-step explanation:

Length of the resulting cuboid

=(12+12)cm

=24cm

Breadth and height remaining the same i.e. 12 cm each

Surface area =2(lb+bh+lh)

=2(24×12+12×12+24×12)cm  

2

 

=1440cm  

2

Answer 2

The total surface area of new cuboid formed by joining of two cubes of edge 12 cm is 1440 cm² .

Option (b) is correct.

Given:

• Two cubes each of edge 12 cm are joined.

To find:

• The surface area of new cuboid is
• (a) 140 cm²
• (b) 1440 cm²
• (c) 144 cm²
• (d) 72 cm²

Solution:

Formula to be used:

Total surface area of cuboid: 2(lb+bh+hl)

here,

l: length

b: breadth

and h: height of cuboid.

Step 1:

Find all dimensions of cuboid.

As two cubes are joined together,

Let these are joined along with their length (as shown in attachment)

Length of cuboid(l)= 24 cm

Breadth (b)= 12 cm

Height (h) = 12 cm

Step 2:

Put the values in the formula.

Total surface area of cuboid: 2(lb+bh+hl)

$= 2(24 \times 12 + 12 \times 12 + 12 \times 24)$

or

$= 2(288 + 144 + 288)$

or

$= 2(720)$

or

Total surface area of cuboid$\bf = 1440 \: {cm}^{2}$

Thus,

The total surface area of new cuboid formed by joining of two cubes of edge 12 cm is 1440 cm² .

Option (b) is correct.

______________________________

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