Question

the area of the four walls in a room is 120 m2. the length of room is twice the breadth. if the height of the room is 4m, find the area of the floor

Answer 1

area of four walls =2(length+breadth)*height

length of room=2b( given in question)

Hence,

120=(2b+b)*4

120=3b*4

120/4=3b

30=3b

b=10m

l=2b=20m

area of floor=l*b

=10*20

200m²

Answer 2

Answer:

Given:-

• Area of four walls of a room is 120m².
• The length is twice the breadth.
• Height of the room is 4m.

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To find:-

• Breadth of the room.

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Solution:-

Let the breadth of the room be b.

Then,

Length of the room will be 2b.

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Note:- Area of four walls means the lateral surface area of the room.

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★ Therefore, we will use the formula of lateral surface area of cuboid.

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$\boxed{\tt{\bigstar{LSA_{(Cuboid)} = 2(l + b) \times h{\bigstar}}}}$

★LSA

(Cuboid)

=2(l+b)×h★

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Here

• l = length
• b = breadth
• h = height

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$\tt:\implies\: \: \: \: \: \: \: \: {LSA = 120}:$

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$\tt:\implies\: \: \: \: \: \: \: \: {2(l + b) \times h = 120}:$

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$\tt:\implies\: \: \: \: \: \: \: \: {2(2b + b) \times 4 = 120}$

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$\tt:\implies\: \: \: \: \: \: \: \: {2(3b) = \dfrac{120}{4}}$

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$\tt:\implies\: \: \: \: \: \: \: \: {6b = 30}:⟹6b=30$

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$\tt:\implies\: \: \: \: \: \: \: \: {b = \dfrac{30}{6}}$

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$\bf:\implies\: \: \: \: \: \: \: \: {b = 5}:⟹b=5$

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Hence,

The breadth of the wall is 5m.

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