The function g is defined by \(\mathrm{g(t) = \frac{6t + 7}{5}}\). What is the value of \(\mathrm{g(8)}\)?
GMAT Advanced Math : (Adv_Math) Questions
The function g is defined by \(\mathrm{g(t) = \frac{6t + 7}{5}}\). What is the value of \(\mathrm{g(8)}\)?
1. TRANSLATE the problem information
- Given information:
- Function: \(\mathrm{g(t) = \frac{6t + 7}{5}}\)
- Need to find: \(\mathrm{g(8)}\)
- What this tells us: We need to substitute \(\mathrm{t = 8}\) into the function definition
2. SIMPLIFY through systematic substitution
- Substitute \(\mathrm{t = 8}\): \(\mathrm{g(8) = \frac{6(8) + 7}{5}}\)
- Work through the numerator first (order of operations):
- Multiply: \(\mathrm{6 \times 8 = 48}\)
- Add: \(\mathrm{48 + 7 = 55}\)
- Now we have: \(\mathrm{g(8) = \frac{55}{5}}\)
- Perform final division: \(\mathrm{55 \div 5 = 11}\)
Answer: C) 11
Why Students Usually Falter on This Problem
Most Common Error Path:
Incomplete SIMPLIFY execution: Students correctly substitute and calculate the numerator (6(8) + 7 = 55), but forget to complete the division by 5.
They see \(\mathrm{g(8) = \frac{6(8) + 7}{5}}\) = \(\mathrm{\frac{48 + 7}{5}}\) = \(\mathrm{\frac{55}{5}}\), but stop at "55" without performing the final division step.
This leads them to select Choice E (55).
Second Most Common Error:
Poor SIMPLIFY organization: Students make arithmetic errors while working through multiple calculation steps, such as incorrectly calculating \(\mathrm{6 \times 8}\) or making addition/division mistakes.
These calculation errors can produce various incorrect results, causing them to select wrong answer choices or become confused and guess.
The Bottom Line:
Function evaluation problems require careful, systematic calculation through multiple arithmetic steps. The key is recognizing that finding \(\mathrm{g(8)}\) means complete substitution followed by thorough simplification—don't stop until you've worked through every operation in the expression.