Advanced MathMediumDimensions of a rectangle from area and a relation
Advanced Math practice question
A rectangle's length is 3 metres more than its width, and its area is 40 square metres. What is the width, in metres?
Answer: 5
w(w + 3) = 40 gives w² + 3w − 40 = (w + 8)(w − 5) = 0, so w = 5 (a width can't be −8).
Common wrong answers
- If you answered 8
- 8 is the LENGTH (5 + 3), or the rejected root's size.
- If you answered 10
- 10 comes from 40 ÷ 4 or a similar slip; check: 10 × 13 = 130, not 40.
- If you answered -8
- −8 is the negative root, impossible for a width.
More Advanced Math questions
- Medium
What are the solutions to x² − 5x + 6 = 0? - Medium
The graph of f(x) = (x − 3)² + 4 is a parabola. What are the coordinates of its vertex? - Medium
If x² − 2x − 8 = (x + 2)(x − a), what is the value of a? - Medium
If √(x + 5) = 4, what is the value of x? - Medium
If f(x) = x + 3 and g(x) = 2x, what is f(g(4))? - Medium
What are the solutions to x² + 6x + 8 = 0?
Not affiliated with the College Board. SAT is a trademark of the College Board.