The length, breadth and height of a room are… | GMAT Sprint

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PS · Problem Solving

705-805

Fractions/Ratios/Decimals

The length, breadth and height of a room are in the ratio 3:2:1. If the breadth and height are halved while the length is doubled, then the total area of the four walls of the room will

Correct answer marked below

remain the same

decrease by 13.64%

decrease by 15%

decrease by 18.75%

decrease by 30%

Correct

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Explanation

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Official Explanation

Official

Let, Initially

Length (L) = 6

Breadth (B) = 4

Height (H) = 2

Total Area of Walls =

2(BH + LH)

2*(4*2 + 6*2)

2*(8+12)

= 40

Then, Finally

Length (L) =

2*6 = 12

Breadth (B) =

4/2 = 2

Height (H) =

2/2 = 1

Total Area of Walls =

2(BH + LH)

2*(2*1 + 12*1)

2*(2+12)

= 28…

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What this question tests

Your ability to convert between fractions, ratios, and decimals and to reason proportionally.

Cross-multiplying incorrectly or mixing up the ratio parts — a part:part ratio is not a fraction of the whole.