Find the perimeter of the rectangle whose length is 40 cm and a diagonal is 41 cm.

Here,

It is given in the question that,

Length of a rectangle = 40 cm

Diagonal of a rectangle = 41 cm

We know that,

Diagonal of a rectangle divides it into two right angled triangles

By using Pythagoras theorem, we get

(Diagonal)^{2} = (Length)^{2} + (Breadth)^{2}

(41)^{2} = (40)^{2} + b^{2}

b^{2} = (41)^{2} – (40)^{2}

b^{2}= 1681 – 1600

b^{2} = 81

b =

b = 9 cm

Thus,

Perimeter of rectangle = 2 (l + b)

= 2 (40 + 9)

= 2 (49)

= 98 cm

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