Question 55

A rectangular field has an area of 20 sq. km. If the perimeter of the field is 18 km, what is the length of the longer side of the field?

Solution

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Let length and breadth of field be $$l$$ and $$b$$ km

Perimeter = $$2(l+b)=18$$

=> $$l+b=9$$ ----------------(i)

Area = $$lb=20$$ ------------(ii)

Substituting value from equation (i), we get : $$l(9-l)=20$$

=> $$l^2-9l+20=0$$

=> $$(l-5)(l-4)=0$$

=> $$l=5,4$$

$$\therefore$$ Length of longest side = 5 km

=> Ans - (D)

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