AlgebraHardPrice of an eraser from two purchases
Algebra practice question
Two notebooks and three erasers cost $9. Four notebooks and one eraser cost $13. What is the price, in dollars, of one eraser?
Answer: 1
From the second purchase, e = 13 − 4n; substituting, 2n + 3(13 − 4n) = 9 gives 10n = 30, so n = 3 and e = 1.
Common wrong answers
- If you answered 2
- 2 averages the two totals badly; check by substitution.
- If you answered 3
- 3 is the price of a notebook.
- If you answered 1.5
- 1.5 divides 9 by 6, treating all items as equal.
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