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The breadth of a prayer hall is $x$ m and its length is $(2x+1)$ m. If its area is $300\text{ m}^2$, what are its dimensions? 
ABreadth $=10$ m, Length $=21$ m
BBreadth $=12$ m, Length $=25$ m
CBreadth $=15$ m, Length $=31$ m
DBreadth $=12.5$ m, Length $=26$ m
Answer & Solution
Correct answer: B. Breadth $=12$ m, Length $=25$ m
The equation is $x(2x+1)=300$, i.e. $2x^2+x-300=0$. Factorising: $2x^2-24x+25x-300=0$, so $(x-12)(2x+25)=0$. This gives $x=12$ or $x=-12.5$. Since breadth cannot be negative, breadth $=12$ m and length $=2(12)+1=25$ m.
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