Riddles, one at a time

Mirror Clock: The Long Wait

How long until the clock shows the next mirror time?

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Answer

4 hours 11 minutes

16:61, 17:71, 18:81 and 19:91 are not real times. The next is 20:02, 4 h 11 min after 15:51.

Old Phone Keys: 4663

Which of the four words types 4663?

Video · Easy Challenge link
Answer

HOME

H is on 4, O on 6, M on 6, E on 3: 4663.

Flip-Flop Gates

Gates start as shown and flip after each box. Where does box 3 land?

Video · Hard Challenge link
Answer

BIN C

After boxes 1 and 2, box 3 goes left, right, right.

Which Tank Fills?

Which tank fills up FIRST?

Video · Hard Challenge link
Answer

E

The cap stops A. Water takes each lowest open pipe: B, then D, then E.

Two Candles: Twice as Tall

Two candles of the same height are lit together and burn at a steady rate. A lasts 4 hours, B lasts 6 hours. After how many hours is B twice as tall as A?

Video · Genius Challenge link
Answer

3 hours

After 3 h, A has 1/4 left and B has 1/2 left: twice.

Hands Apart: 9:45

What is the SMALLER angle between the hands?

Video · Genius Challenge link
Answer

22.5°

The minute hand is on 9; the hour hand is 3/4 of the way to 10: 3/4 × 30° = 22.5°.

Challenge link