195.
A farmer wishes to grow a 100 m2 rectangular vegetable garden. Since he has with the only 30 m barbed wire, he fences three sides of the rectangular garden letting compound wall of his house act as the four the side-fence. Find the dimension of his garden.
Let the length of one side be x meters and other side by y meters. Then,
x + y + x = 30 ...(i)
⇒ y = 30 – 2x
∴ Area of the vegetable garden = 100 m
2
⇒ xy = 100

⇒ xy = 100
⇒ x (30 – 2x) = 100
⇒ 30x – 2x2 = 100
⇒ 15x – x2 = 50
⇒ x2 – 15x + 50 = 0
⇒ x2 – 10x – 5x + 50 = 0
⇒ (x – 10) (x – 5) = 0
⇒ x = 5, 10
When x = 5, we have
y = 30 – 2 x 5 = 20
When x = 10, we have
y = 30 – 2 x 10= 10
Hence, the dimensions of the vegetable garden are
5 m x 20 m or 10 m x 10 m.
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