Four quick brain teasers
✓ With solution
Some pills, a brick, lilies on a lake and a single match: short questions that need a calm mind.
A doctor gives you 3 pills and says: take one every half hour. How long after the first pill do you take the last one?
- AHalf an hour
- BAn hour
- CAn hour and a half
- DTwo hours
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Answer: B) An hour. You take the first pill straight away, the second half an hour later, and the third half an hour after that. From the first to the last is just one hour. The trap is multiplying 3 by half an hour, when there are only two gaps between three pills.
A brick weighs 1 kg plus half a brick. How much does the brick weigh?
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A brick is two halves. If a brick = 1 kg + half a brick, what must the other half weigh?
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Answer: 2 kg. A brick is two halves: one is the "half a brick" in the question, and the other must be the 1 kg. So half a brick weighs 1 kg and the whole brick weighs 2 kg. Check: 1 kg + half a brick (1 kg) = 2 kg. The quick wrong answer is 1.5 kg.
A patch of water lilies on a lake doubles in size every day. On day 30 it covers the whole lake. On which day did it cover half the lake?
- ADay 15
- BDay 20
- CDay 28
- DDay 29
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Answer: D) Day 29. The patch doubles every day, so the day before it covered the whole lake it was half that size: half the lake on day 29. Day 15 would only be right if it grew by the same amount each day, not if it doubles.
You walk into a cold, dark hut with just one match. In the hut there is a candle, a wood stove and an oil lamp. What do you light first?
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Before anything in the hut can be lit, what has to be burning?
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Answer: The match. The match! You can't light the candle, the stove or the lamp until you have lit the match itself.
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