Question

Question 5 Is it possible to design a rectangular park of perimeter 80 and area 400 m^2 ? If so find its length and breadth.

Class 10 - Math - Quadratic Equations Page 91

Answer 1

Hey there!

Let the breadth be = x
Length = 40 - x

Area = 400 m^2
l × b = 400
(x)(40 - x) = 400

x^2 - 40x + 400 = 0
By using Identity,
(a-b)^2 = a^2 - 2ab + b^2

(x-20)^2

COMPLETE SOLUTION IS DONE IN THE ABOVE PIC.

Hope it helped
#EshanSingh1

Answer 2

Let the length and breadth of the park be l and b.
Perimeter = 2 (l + b) = 80
l + b = 40
Or, b = 40 - l
Area = l×b = l(40 - l) = 40l - l240l -  l2 = 400
l2 -  40l + 400 = 0
Comparing this equation with al2 + bl + c = 0, we get
a = 1, b = -40, c = 400
Discriminant = b2 - 4ac
(-40)2 - 4 × 400
= 1600 - 1600 = 0
b2 - 4ac = 0
Therefore, this equation has equal real roots. And hence, this situation is possible.
Root of this equation,l = -b/2a
l = (40)/2(1) = 40/2 = 20
Therefore, length of park, l = 20 m
And breadth of park, b = 40 - l = 40 - 20 = 20 m.