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 + b2
b2 = (41)2 – (40)2
b2= 1681 – 1600
b2 = 81
b = 
b = 9 cm
Thus,
Perimeter of rectangle = 2 (l + b)
= 2 (40 + 9)
= 2 (49)
= 98 cm
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