A park ranger hung squirrel houses each in the shape of a right rectangular prism for fox squirrels. Each house...
GMAT Advanced Math : (Adv_Math) Questions
A park ranger hung squirrel houses each in the shape of a right rectangular prism for fox squirrels. Each house has a height of \(\mathrm{11}\) inches. The length of each house's base is \(\mathrm{x}\) inches, which is \(\mathrm{1}\) inch more than the width of the house's base. Which function \(\mathrm{V}\) gives the volume of each house, in cubic inches, in terms of the length of the house's base?
\(\mathrm{V(x) = 11x(x - 1)}\)
\(\mathrm{V(x) = 11x(x + 1)}\)
\(\mathrm{V(x) = x(x + 11)(x - 1)}\)
\(\mathrm{V(x) = x(x + 11)(x + 1)}\)
1. TRANSLATE the problem information
- Given information:
- Each house is a right rectangular prism
- \(\mathrm{Height = 11\ inches}\)
- \(\mathrm{Length\ of\ base = x\ inches}\)
- Length is 1 inch more than the width
- What this tells us: We need to express width in terms of x
2. TRANSLATE the length-width relationship
- "Length is 1 inch more than width" means:
- \(\mathrm{Length = Width + 1}\)
- Since \(\mathrm{Length = x}\), we have: \(\mathrm{x = Width + 1}\)
- Therefore: \(\mathrm{Width = x - 1}\)
3. INFER the volume calculation approach
- For any rectangular prism: \(\mathrm{Volume = length \times width \times height}\)
- We need to substitute our known values to get a function \(\mathrm{V(x)}\)
4. SIMPLIFY by substituting values
- \(\mathrm{V = length \times width \times height}\)
- \(\mathrm{V = x \times (x - 1) \times 11}\)
- \(\mathrm{V = 11x(x - 1)}\)
Answer: A. \(\mathrm{V(x) = 11x(x - 1)}\)
Why Students Usually Falter on This Problem
Most Common Error Path:
Weak TRANSLATE skill: Misinterpreting "length is 1 inch more than width"
Students often think this means \(\mathrm{width = x + 1}\) instead of \(\mathrm{width = x - 1}\). They reverse the relationship, thinking "if length is more than width, then width must be x + 1." This fundamental translation error leads them to calculate \(\mathrm{V = 11x(x + 1)}\).
This leads them to select Choice B (\(\mathrm{V(x) = 11x(x + 1)}\))
The Bottom Line:
The key challenge is carefully translating the verbal relationship between length and width. The phrase "A is more than B" means \(\mathrm{A = B + (amount)}\), so when length is 1 more than width and \(\mathrm{length = x}\), we get \(\mathrm{x = width + 1}\), which means \(\mathrm{width = x - 1}\).
\(\mathrm{V(x) = 11x(x - 1)}\)
\(\mathrm{V(x) = 11x(x + 1)}\)
\(\mathrm{V(x) = x(x + 11)(x - 1)}\)
\(\mathrm{V(x) = x(x + 11)(x + 1)}\)