What is the area, in square inches, of a rectangle with a length of 7 inches and a width of...
GMAT Geometry & Trigonometry : (Geo_Trig) Questions
What is the area, in square inches, of a rectangle with a length of 7 inches and a width of 6 inches?
1. TRANSLATE the problem information
- Given information:
- Rectangle length: 7 inches
- Rectangle width: 6 inches
- Need to find: area in square inches
2. INFER the approach needed
- To find area of a rectangle, we need to use the area formula
- Area formula: \(\mathrm{A = length \times width}\)
- We have both dimensions, so we can substitute directly
3. Apply the formula and calculate
- \(\mathrm{A = length \times width}\)
- \(\mathrm{A = 7 \times 6 = 42}\)
- The area is 42 square inches
Answer: C. 42
Why Students Usually Falter on This Problem
Most Common Error Path:
Weak TRANSLATE reasoning: Students misunderstand what "area" means and think it requires adding the dimensions instead of multiplying them.
Instead of recognizing that area measures the space inside a shape (requiring \(\mathrm{length \times width}\)), they treat it like perimeter or just combine the numbers by adding: \(\mathrm{7 + 6 = 13}\).
This leads them to select Choice A (13).
Second Most Common Error:
Conceptual confusion about area: Students may remember that rectangle calculations involve both dimensions but apply an incorrect operation or make calculation errors.
Some students might double their work or misremember a formula step, leading to calculation errors that could result in other incorrect choices like Choice D (84) or getting confused and guessing.
The Bottom Line:
This problem tests the most fundamental geometric calculation - rectangle area. The key challenge is that students must clearly understand that "area" specifically means multiplying the two dimensions, not adding them or applying any other operation.