Riddles, one at a time
Robot Program: Five Commands
Straight arrow: 1 tile forward. Curved arrow: turn on the spot, to its own left or right. Which tile does it stop on?
Turns use the robot's own left and right, and a turn does not move it.
Video · Easy
Challenge link
Answer
C
Up 2, turn right, then 2 forward: it stops on C.
100 Days Later
What day will it be 100 days from today?
Take away whole weeks: 100 = 98 + 2.
Video · Medium
Challenge link
Answer
Monday
100 = 14 weeks (98 days) + 2 days. Saturday + 2 = Monday.
Read the Clocks
What time does clock 4 show?
almost
Answer
7:55
Each clock is 1 hour 35 minutes later.
Climbing Robot
A robot climbs a 10 m wall. Each day it climbs 3 m; each night it slips back 2 m. On which day does it reach the top?
On the last day it does not slip back.
Video · Genius
Challenge link
Answer
Day 8
After night 7 it is at 7 m; day 8 takes it to 10 m.
Gem Finder: The Gem Field
A number counts the gems in the 8 tiles around it; numbered tiles have none. Which lettered tile hides a gem?
Start with the 0 in the bottom-left corner.
Video · Expert
Challenge link
Answer
B
The bottom-left 0 makes C empty. The 1 above it touches only B and C, so B holds the gem.
Which Ring? Three Rings
Which tile belongs in the very centre?
It must be round, blue and have a dot.
Video · Medium
Challenge link
Answer
D
Only D is round, blue AND has a dot.
Challenge link
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