Area and Perimeter Practice Test 1

Question : 2 of 40

Marks: +1, -0

The length of a rectangle is decreased by r% and breadth is increased by (r + 5)%. If the area of the rectangle is unaltered then find the value of r.

Validate

Solution:

Here,

(100-r)/{100} l × (100+r+5)/{100} ×b

= lb
⇒ (100 – r) (105 + r) = 10000
⇒ 10500 – 105r + 100r +

r^2

= 10000
⇒

r^2

+ 5r – 500
⇒ (r + 25) (r – 20) = 0
Hence, r = 20

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