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6 bottles of juice cost 42 yuan: 10 bottles?
At a supermarket, 6 bottles of juice cost 42 yuan in total. At the same unit price, how much do 10 bottles of juice cost?
Answer
70
Step-by-step
- 42 ÷ 6 = 7Find the unit price first (reduce to one)
- 7 × 10 = 70Unit price × quantity
Why it works
The price of one bottle is the total cost divided by the number of bottles; when the unit price stays the same, the total cost grows in proportion to the number of bottles.
Common mistakes
- Dividing 42 by 10 instead of by the 6 bottles bought.
- Adding 7 to 42 after finding 7 yuan per bottle instead of multiplying 7 by 10.