Riddles, one at a time
Two Candles: 20 cm and 15 cm
After how many hours are they the same height?
How big is the gap at the start, and how fast does it close?
Video · Hard
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2 hours
After 2 h: A is 20 − 8 = 12 cm, B is 15 − 3 = 12 cm.
Fold, Fold, Punch
Which pattern appears when it is opened?
Video · Hard
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D
Each fold mirrors the holes across its crease.
Mirror Odometer: 15951
How many more km until the next mirror number?
The middle digit is already 9, so it cannot go up. What has to change instead?
Video · Medium
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110 km
The next mirror number is 16061: 16061 − 15951 = 110.
Old Phone Keys: 4663
Which of the four words types 4663?
Find each digit's letters on the keypad. Only one of the four fits.
Video · Easy
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HOME
H is on 4, O on 6, M on 6, E on 3: 4663.
Fewest Tokens: Pay 11
Which tokens pay 11 with the fewest tokens?
Biggest first is not always fewest. Try every pair.
Video · Hard
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5 + 6
Just 2 tokens. Biggest first, 9 + 1 + 1, needs 3.