A rectangular room has an area of 300 square units, and its length is 10 units more than its breadth. What is the breadth of the room?

Correct answer: 15

Let the breadth of the room be \(x\) units. Then its length is \(x+10\) units. Using the area, \(x(x+10)=300\), so \(x^2+10x-300=0\). Factoring gives \((x-15)(x+20)=0\), hence \(x=15\) or \(x=-20\). Since a length cannot be negative, the breadth is 15 units. In word problems, always reject roots that are not physically meaningful.