AlgebraHardClass size from two fractional groups
Algebra practice question
In a class, one quarter of the students come by bus and one third walk. Together, the students who come by bus or walk number 7. How many students are in the class?
Answer: 12
Let n be the class size: n/4 + n/3 = 7. Common denominator 12: 7n/12 = 7, so n = 12.
Common wrong answers
- If you answered 21
- 21 comes from n/3 = 7 alone, ignoring the bus riders.
- If you answered 49
- 49 comes from n/7 = 7, adding the denominators instead of finding a common one.
- If you answered 84
- 84 multiplies 7 by 12 without dividing by the combined coefficient 7.
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