Riddles, one at a time
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?
A loses a quarter of its height each hour, B loses a sixth.
3 hours
After 3 h, A has 1/4 left and B has 1/2 left: twice.
Glass Overlay: Lines Cancel
Which card completes the grid?
Lines that appear on both cards disappear; all the other lines stay.
B
In each row, lines on both cards cancel and the rest stay. Row 3 gives card B.
Lighthouse Flashes
A lighthouse flashes evenly. From the 1st flash to the 6th takes 5 seconds. How long from the 1st flash to the 11th?
Count the gaps between flashes, not the flashes.
10 seconds
Flash 1 to flash 6 is 5 gaps, so each gap is 1 second. Flash 1 to 11 is 10 gaps.
Word Ladder: Tool to Book
COOK
COOL to COOK changes L to K; COOK to HOOK changes C to H.
Crack the Lock
Which 3-digit code opens the lock?
738
3 sits in the middle, 8 stays last, 7 goes first.