If the rectangular floor is 300*350 feet, the area of the floor is 105000 square feet.

If the width remains fixed,

how many feet must be added to length s.t the floor area increases by 20%(\(\frac{1}{5}\))

The increased area is \(\frac{6}{5}*105000 = 6*21000 = 126000\) (because \(1+\frac{1}{5}= \frac{6}{5}\))

Let the increased length be x.

Since the width remains the same, 300*x= 126000

x = 1260/3 = 420 which is an increase of 420-350=

70(Option D)P.S there are easier ways to do these questions. These lengthy calculation needn't be done.

More often than not in such questions, the common terms will cancel each other out

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