Question

The length of a rectangle is three times its width if the perimeter is 84 m find the length of a rectangle

Answer 1

let the width be x then length = 3x
perimeter = 2(l+b)=84m
2(l+b) = 84
2(3x+x) = 84
4x = 84/2 = 42
x=42/4 = 10.5m
length is 3x = 3×10.5 = 31.5 m
hope this helps

Answer 2

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$\huge{\underline{\underline{\sf{\blue{SOLUTION:-}}}}}$

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$\sf{\underline{\green{AnswEr:-}}}$

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• The length of the rectangle = 31.5 Cm

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$\sf{\underline{\green{Given:-}}}$

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• The length of a rectangle is three times its width. if the perimeter is 84.

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$\sf{\underline{\green{Find:-}}}$

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• The length of rectangle = ?

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$\sf{\underline{\green{Explanation:-}}}$

Let the breadth be y.

$\:\:\:\:\dag\bf{\underline{\underline \red{Then:-}}}$

• Length = 3y

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$\:\:\:\:\dag\bf{\underline{\underline \red{Now:-}}}$

$\sf\underline{\purple{\:\:\: Perimeter = 2 \times (Length + Breadth)\:\:\:}}$

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$\sf{Perimeter = 2 \times (3y+ y)}$

$\sf{Perimeter = 2 \times (4y)}$

$\sf{Perimeter = 8y }$

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$\sf{\underline\pink{A.T.Q:-}}$

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$\longrightarrow \sf {4y + 40 = 100}$

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$\longrightarrow \sf {8y = 84}$

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$\longrightarrow \sf {y = \cancel\dfrac{84}{8} }$

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$\longrightarrow \sf {y = \dfrac{21}{2}}$

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$\:\:\:\:\dag\bf{\underline{\underline \red{Hence:-}}}$

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• Length of rectangle = $\sf{\dfrac{21}{2} \times 3\:Cm}$

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• Length of rectangle = $\sf{\dfrac{63}{2} }$

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• Length of rectangle = 31.5 Cm

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$\rule{200}{2}$