A rectangle has length x + 3 and width x. Which expression gives its area?
- x^2 + 3x
- 2x + 3
- x^2 + 3
- 3x^2
Show answer and explanation
Answer: x^2 + 3x
Area is length times width, so x(x + 3) = x^2 + 3x.
SAT Math skill page
Translate word problems into quadratics, then use the form that answers the question fastest.
What this tests
Practice examples
A rectangle has length x + 3 and width x. Which expression gives its area?
Answer: x^2 + 3x
Area is length times width, so x(x + 3) = x^2 + 3x.
A ball height is modeled by h = -t^2 + 6t. At what positive time is the height 0?
Answer: 6
Set -t^2 + 6t = 0, factor t(6 - t) = 0, and use the positive nonzero time t = 6.
A quadratic has zeros 2 and 8. What is the x-coordinate of its vertex?
Answer: 5
The vertex lies halfway between the zeros, so (2 + 8) / 2 = 5.
Quick drills
Pause before the answer choices, write the rule or setup you need, then check whether the question is asking for the value, the relationship, or the best-supported conclusion.
Pause before the answer choices, write the rule or setup you need, then check whether the question is asking for the value, the relationship, or the best-supported conclusion.
Pause before the answer choices, write the rule or setup you need, then check whether the question is asking for the value, the relationship, or the best-supported conclusion.
Pause before the answer choices, write the rule or setup you need, then check whether the question is asking for the value, the relationship, or the best-supported conclusion.
Avoid these traps
The SAT often hides the real skill inside familiar wording. Identify the rule, relationship, or question type first.
Many wrong answers are close. Check every condition in the question before committing.
Reread what the question asks for so you do not answer a nearby but different question.
Study plan
Related practice
Skill cluster
FAQ
Start with a few focused examples, review the mistake pattern, then mix the skill into full SAT practice so you can recognize it in context.
It shows up in short, high-leverage questions where one missed rule or setup can quickly cost a point.
Yes. Dolphin SAT can surface targeted practice, track missed questions, and help you review the patterns that keep repeating.