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The perimeter of a rectangular board is 70 cm. Taking its length as x cm, find its width in terms of x.If the area of the rectangular board is 300 cm2; find its dimensions. - Mathematics

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Question

The perimeter of a rectangular board is 70 cm. Taking its length as x cm, find its width in terms of x.
If the area of the rectangular board is 300 cm2; find its dimensions.

Sum
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Solution

Let b be the breadth of the rectangle. then its perimeter

2(x + b) = 70

x + b = 35

b = 35 - x

Again

x × b = 300

x(35 - x) = 300

35x - x2 = 300

0 = x2 - 35x + 300

(x - 15) (x - 20) = 0

x = 15, 20

Hence, its length is 20 cm and width is 15 cm.

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Chapter 20: Area and Perimeter of Plane Figures - Exercise 20 (B) [Page 256]

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Selina Concise Mathematics [English] Class 9 ICSE
Chapter 20 Area and Perimeter of Plane Figures
Exercise 20 (B) | Q 28 | Page 256
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