Riddles, one at a time
Gem Finder: Hidden Gems
A number counts the gems in the 8 tiles around it; numbered tiles have none. Which lettered tile hides a gem?
Start with the 0s and 1s: they tell you which tiles are empty.
C
The bottom-right 2 touches just two covered tiles, C and its neighbour, so both hide gems. A, B, D are empty.
Old Phone Keys: Same as BOOK
Which of the four words types the same number as BOOK?
Type BOOK first, then compare each option key by key.
COOK
B and C share key 2, so BOOK and COOK both type 2665.
Open the Tap
Valves stay as shown. Which jar fills with water?
JAR C
Every other route ends at a closed valve.
Fewest Tokens: Pay 24
Which tokens pay 24 with the fewest tokens?
Biggest first is not always fewest. A token can be used many times.
6 + 6 + 6 + 6
Just 4 tokens. Biggest first, 15 + 6 + 1 + 1 + 1, needs 5.
Split 8 Litres
Fewest pours to share it 4 L and 4 L?
Only the 8 L and 5 L jugs can end with 4 L. Use the 3 L jug as a measure.
7 pours
8→5, 5→3, 3→8, 5→3, 8→5, 5→3, 3→8: 4 L and 4 L.