AlgebraEasy–MediumTwo kinds of book from a total and a difference
Algebra practice question
A shelf holds 10 books, all of them novels or atlases. There are 4 more novels than atlases. How many atlases are on the shelf?
- A. 3Correct
- B. 7
- C. 6
- D. 4
Answer: A. 3
Let atlases be a: a + (a + 4) = 10, so 2a = 6 and a = 3. (There are 7 novels.)
Why the other answers are wrong
- B. 7
- 7 is the number of novels.
- C. 6
- 6 is 10 − 4, forgetting to halve.
- D. 4
- 4 is the difference, not a count.
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