A group of monarch butterflies migrated from Chicago, Illinois, to Michoacán, Mexico, flying a total of 2,100 miles. It took...
GMAT Problem-Solving and Data Analysis : (PS_DA) Questions
A group of monarch butterflies migrated from Chicago, Illinois, to Michoacán, Mexico, flying a total of 2,100 miles. It took a single butterfly in the group 120 days to travel this route one way. On average, how many miles did the butterfly travel per day?
1. TRANSLATE the problem information
- Given information:
- Total distance traveled: 2,100 miles
- Total time taken: 120 days
- Find: Average miles traveled per day
- What this tells us: We need to find a rate (miles per day)
2. INFER the approach
- This is asking for an average rate of travel
- To find "per day" we divide the total by the number of days
- Set up: Miles per day = Total miles ÷ Total days
3. SIMPLIFY the calculation
- Miles per day = \(2{,}100 \div 120\) (use calculator)
- Miles per day = \(17.5\)
Answer: C. 17.5
Why Students Usually Falter on This Problem
Most Common Error Path:
Weak TRANSLATE skill: Students may set up the division backwards, calculating days per mile instead of miles per day.
They might compute \(120 \div 2{,}100 = 0.057\), thinking this gives them the rate. This leads them to select Choice A (0.057).
Second Most Common Error:
Poor SIMPLIFY execution: Students set up the problem correctly but make arithmetic errors during division.
Common mistakes include decimal point placement or incorrect long division steps. This may lead them to select Choice B (0.729) or causes them to get stuck and guess.
The Bottom Line:
Rate problems require careful attention to which quantity goes in the numerator and which goes in the denominator. The phrase "miles per day" means miles divided by days, not the reverse.