Question

Find the length of the rectangular field whose perimeter is 90 metres and breadth is 20 metres.​

Answer 1

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Refer to the attachment

Answer 2

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Let x be the length

2 ( l + b ) = Perimeter

L = length and B = breadth

$\sf = 2(x + 20) \\ \sf = 2x + 40 \\ \\ \sf = 2x + 40 = 90 \\ \sf = 2x = 90 - 40 \\ \sf = 2x = 50 \\ \sf = x = \frac{50}{2} \: ( \: cancelling \: ) \\ \sf =( x = 25)$

Verification

$\sf =l = 25 \\ \sf =b = 20 \\ \sf =p = 2(l + b) \\ \sf =2(25 + 20) \\ \sf =2(45) = 2 \times 45 \\ \sf = 90$

Therefore, 90 is the length of the rectangular field.