Mrs Lim, a librarian, had some books on a shelf. In the morning, 36 books were returned to the shelf. In the afternoon, 25 of the books on the shelf were borrowed. After that, 48 books remained on the shelf. How many books were on the shelf at first?
- 44
- 80
- 116
- 156
Need a hint?
Find the number of books on the shelf before the afternoon borrowing first. The 48 books left represent 35 of that number.
Worked answer
- After 25 of the books were borrowed, 35 of them remained.
- 35 of the books = 48, so 15 = 48 ÷ 3 = 16.
- Books on the shelf before the borrowing = 5 × 16 = 80.
- These 80 books include the 36 books returned in the morning.
- Books on the shelf at first = 80 − 36 = 44.
Answer: 44 books
The mistake this question tests
Habit
Fraction of a remainder
Some pupils may add the 36 returned books to the 80 books present after the return. The returned books were already included in those 80 books, so the initial number was smaller.
How to fix it at home →Wrong answers children often give:
- 80 Calculation slip
- 84 Fraction of a remainder
- 116 Calculation slip
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