Question

b. two cubes each of edge 5 cm are joined face to face. The surface area of the cuboid. Thus

formed is:

i. 200cm2

ii. 250cm2

iii. 360cm2

iv. 400cm2​

Answer 1

Answer:

The surface area of cuboid is 250 cm².

Explanation :

If two cubes, each of edge 5 cm are joined, then the length (l) of the resulting cuboid will become (2×5)cm = 10cm.

The breadth (b) and height (h) will remain 5 cm.

So, the dimensions of the resulting cuboid will be 10 cm ×5 cm ×5 cm.

We know, surface area (S.A.)of a cuboid is given as:

SA = 2(lb + bh + lh) where l is the length, b is the breadth and h is the height.

Putting their respective values, we get Surface area as:

2(10×5+ 5×5+ 10×5) cm²

= 2 (50 + 25 + 50) cm²

= 2 (125) cm²

= 250 cm²

So, surface area is 250 cm².

Answer 2

Answer:

ii)Side of each cube = 5 cm

When they are joined they become cuboid.

Length of cuboid = 10 cm

Breadth of cuboid = 5 cm

Height of cuboid = 5 cm

Lateral/ Curved Surface Area of cuboid

= 2(l+b) h

= 2×(10+5)×5

= 2× 15×5

= 150 cm^2

Total Surface Area of cuboid

= 2(lb+lh+bh)

= 2(10×5+10×5+5×5)

= 2(50+50+25)

=2×125

= 250 cm^2.

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iii) The surface area of cuboid is 360 cm².

If two cubes, each of edge 6 cm are joined, then the length (l) of the resulting cuboid will become (2×6)cm = 12cm.

The breadth (b) and height (h) will remain 6 cm.

So, the dimensions of the resulting cuboid will be 12 cm ×6 cm ×6 cm.

We know, surface area (S.A.)of a cuboid is given as:

SA = 2(lb + bh + lh) where l is the length, b is the breadth and h is the height.

Putting their respective values, we get Surface area as:

2(12×6 + 6×6 + 12×6) cm²

= 2 (72 + 36 + 72) cm²

= 2 (180) cm²

= 360 cm²

So, surface area is 360 cm².

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