AlgebraMediumTwo prices, a count and a total
Algebra practice question
A stall sells pens for $3 each and notebooks for $2 each. A customer buys 20 items for a total of $52. How many pens did the customer buy?
Answer: 12
Let p be pens and n notebooks: p + n = 20 and 3p + 2n = 52. From the first, n = 20 − p; substitute: 3p + 40 − 2p = 52, so p = 12. Check: 12 pens ($36) + 8 notebooks ($16) = $52.
Common wrong answers
- If you answered 8
- 8 is the number of NOTEBOOKS. The question asks for pens.
- If you answered 17
- 17 is about 52 / 3, treating every item as a pen. Notebooks account for part of the total.
- If you answered 26
- 26 is 52 / 2, treating every item as a notebook.
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