Question 88
HardOriginal questionA 50-litre drum is full of pure mustard oil. Every morning 5 litres are drawn off and replaced with a cheaper oil.
After how many mornings does the pure mustard oil first fall below 40 litres?
Show the answer and explanation
CorrectNot quiteAnswer B
Correct answer: B
Explanation
After 2 mornings: 40.5 litres, still not below 40.
After 3 mornings: 36.45 litres, below 40.
Worth noting
2 mornings would be the answer if pure oil were removed each time; the cheaper oil drawn out slows the fall.
- Concept
- The number of replacements
- Typical timeTypical
- 150 s
- Your timeYours
- —
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