The length of a rectangular poster is 10 cm more than its breadth. If its area is 375 square cm, what is its breadth?

Correct answer: 15 cm

Let the breadth be \(x\) cm. Then the length is \(x+10\) cm, so the area condition gives \(x(x+10)=375\), or \(x^2+10x-375=0\). Factoring gives \((x-15)(x+25)=0\). Thus \(x=15\) or \(x=-25\); a dimension cannot be negative, so the breadth is 15 cm. The value 25 cm is the length, not the breadth. Exam tip: verify the result using \(15\times25=375\).