GED Mathematical Reasoning TestQuantitative Problem Solving with Rational NumbersMedium
A car's fuel tank is 5/6 full. After a trip, it is now 1/3 full. What fraction of the tank's capacity was used during the trip?
- A1/6
- B1/2
- C2/3
- D1/3
Show answer & explanationAnswer & explanation
Correct answer: B. 1/2
To find the fraction used, subtract the final fraction from the initial fraction: 5/6 - 1/3. First, find a common denominator for 6 and 3, which is 6. Convert 1/3 to 2/6. Then, 5/6 - 2/6 = 3/6, which simplifies to 1/2.
Why the other options are wrong
- A. This is an incorrect calculation, possibly a mis-subtraction or mis-simplification.
- C. This is an incorrect calculation, possibly by adding instead of subtracting or other error.
- D. This is the final amount, not the amount used.
Subtracting Fractions with Unlike Denominators
To subtract fractions with different denominators, first find a common denominator, convert both fractions to equivalent fractions with that common denominator, and then subtract the numerators while keeping the common denominator.
- Find the least common multiple (LCM) of the denominators.
- Convert each fraction to an equivalent fraction with the LCM as denominator.
- Subtract the numerators and keep the common denominator.
- Simplify the resulting fraction if possible.
Memory trick: Start minus end, common ground, difference found.