Q: The length of a rectangle is 4 cm longer than the width. If the rectangle’s area is 45 cm², what is the width?
Answer: 5 cm
Explanation: Call the width x. Then, the length is x+4.
Area of a rectangle = (length)(width).
45 = x(x+4)
45 = x² + 4x
0 = x² + 4x – 45
0 = (x + 9)(x – 5)
x = -9 or x = 5
Since a length can’t be negative, discard x = -9. The only solution is x = 5. Since ‘x’ is what we called the width, it is the answer to the question. Just put the appropriate unit on it: 5 cm.