AlgebraHardTwo-variable system from training times
Algebra practice question
Leo's training session of 3 laps and 4 sprints takes 20 minutes, and a session of 5 laps and 2 sprints takes 24 minutes. Each lap takes the same time, and each sprint takes the same time. How many minutes does one lap take?
Answer: 4
Let a lap take L minutes and a sprint S: 3L + 4S = 20 and 5L + 2S = 24. Doubling the second gives 10L + 4S = 48; subtracting the first gives 7L = 28, so L = 4 (and S = 2).
Common wrong answers
- If you answered 2
- 2 is the time for a sprint, not a lap.
- If you answered 6
- 6 is a lap plus a sprint.
- If you answered 28
- 28 is 7L before dividing by 7.
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