Riddles, one at a time

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?

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.

One Stroke: House

Without lifting your pen and without going over any line twice, which figure can you draw?

Video · Medium Challenge link
Answer

B

Only B has just 2 dots where an odd number of lines meet: start at one, end at the other.

Growing Diamond

Steps 6 and 7 are not shown. How many tiles will step 8 have?

Video · Expert Challenge link
Answer

113

Step 8 is an 8 × 8 grid woven with a 7 × 7 grid: 64 + 49 = 113 tiles.

Lamp Code: Deduce the Lamps

What number does the last row show?

Video · Expert Challenge link
Answer

14

Lamps worth 8, 4, 2, 1 fit every row: 2 + 1 = 3, 4 + 1 = 5, 8 + 1 = 9, 4 + 2 = 6. So 8 + 4 + 2 = 14.

The Stone Garden

Which gate leads to the fountain?

Video · Easy Challenge link
Answer

GATE C

Every other gate is sealed off by a stone wall.

Shaded Part: The Triangle

What fraction of the square is gold?

Video · Medium Challenge link
Answer

1/2

The triangle has the full base and full height of the square, so it is half: 8 of 16 squares.

Challenge link