Question

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

Answer 1

Hey!!! Here is your answer !!! As you know, Perimeter of a rectangle = 2(length + breadth) So first we need to find the breadth as we have the diagonal and length with us....(diagonal is the hypotenuse) Therefore,by Pythagorean theorem, (P)^2+(B)^2=(H)^2 So, (40)^2+(P)^2 = (41)^2 So, 1600+(P)^2 = 1681 So, (P)^2 = 81 So, P = 9cm Now, Perimeter of a rectangle = 2(l+b)                                           =2(40+9)                                           =2(49)                                           =98cm

Answer 2

The diagonal of the rectangle divides it into two right-angled triangles, so we can use the pythagorean theorem to solve this problem. 
41cm is the diagonal and 40cm is the length.
hyp² = length² + breadth²
41²   = 40² + breadth²
1681 = 1600 + breadth²
1681 - 1600 = breadth²
breadth² = 81
breadth = √81
= 9cm
Perimeter = 2( l + b )
               = 2 * (40 + 9)
               = 2 * 49
               = 98cm
The perimeter of the rectangle is 98cm.