Advanced MathHardValue of an expression from a ratio
Advanced Math practice question
If a/b = 4, where a and b are positive, what is the value of (a² − b²)/(ab)?
Answer: 15/4 or 3.75
Divide numerator and denominator by b²: (a² − b²)/(ab) = ((a/b)² − 1)/(a/b) = (16 − 1)/4 = 15/4.
Common wrong answers
- If you answered 3
- 3 uses 4 − 1 without squaring.
- If you answered 4
- 4 is a/b itself.
- If you answered 15
- 15 is (a/b)² − 1, forgetting to divide by a/b.
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