Question

The perimeter of a rectangle is 240cm. If it's length is inreased by 10% and breadth is decreased by 20%, we get the same perimeter. Find the length and the breadth of the rectangles

Answer 1

Answer:

Length = 80 cm,   Breadth = 40 cm

Step-by-step explanation:

Old perimeter = 240 cm

Length = l

Breadth = b

Perimeter = 2(length + breadth)

240 = 2(l + b)

240/2 = l + b

120 = l + b

120 - l = b   ---------------------------(1)

New perimeter = Old perimeter = 240 cm

New length = l + 10%l = l + (10/100)l = 110l/100

New breadth = b - 20%b = b - (20/100)b = 80b/100

Perimeter of rectangle = 2(length + breadth)

240 = 2(110l/100 + 80b/100)

240/2 = 11l/10 + 8b/10

120 = (11l + 8b)/10

1200 = 11l + 8b

By substituting value of b

1200 = 11l + 8(120 - l)

1200 = 11l + 960 - 8l

1200 - 960 = 3l

240 = 3l

240/3 = l

l = 80 cm

Putting value of l in equation(1)

120 - l = b

120 - 80 = b

b = 40cm

Hope it helps.

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