The perimeter of a rectangle is 68 cm. If the area of the rectangle is 240 cm2, then what is the length of each of its diagonals ?
Answer & explanation
Correct answer: option 3
We know that,
Pythagoras theorem: Perpendicular2 = Length2 + Breadth2
Perimeter of Rectangle = 2(l + b)
We have,
Perimeter of a rectangle = 68 cm
Area of the rectangle = 240 cm2
So, 2(l + b) = 68
l + b = 34 ------ (A)
Area of rectangle = l × b
= l × b = 240 ------ (B)
From (1), we get l = 34 – b,
Then, (34 – b) × b = 240
= b2 – 34b + 240 = 0
= b2 – 10b – 24b + 240 = 0
= b(b – 10) – 24(b – 10) = 0
= (b – 24)(b – 10) = 0
= b = 10 or 24
Then, Length = 24 or 10 cm
Length of diagonal = \(\sqrt {24^2 + 10^2}\) = 26cm