A stationery shop is running a special offer: Buy 4 notebooks and get 1 notebook free. Priya wants to buy 30 notebooks for her reading club. Each notebook costs $m. How much will she pay for the notebooks? Express your answer in terms of m.
Need a hint?
Each set of 5 notebooks contains 4 that Priya must pay for.
Worked answer
- 30 ÷ 5 = 6, so the notebooks form 6 groups of 5.
- She pays for 6 × 4 = 24 notebooks.
- 24 notebooks × $m each = $24m.
Answer: 24m
The mistake this question tests
Habit
Factors and multiples (HCF, LCM)
Multiplying 30 by m charges Priya for every notebook and ignores the free notebook. She pays for only 4 notebooks in each set of 5.
How to fix it at home →Wrong answers children often give:
- $30m Calculation slip
- $6m Factors and multiples (HCF, LCM)
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