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Riddles, one at a time

After how many hours are they the same height?

Video · Expert Challenge link
Answer

5 hours

After 5 h: A is 32 − 20 = 12 cm, B is 22 − 10 = 12 cm.

A melon weighs 2 kg plus one third of its own weight. How much does the melon weigh?

Text · Easy Challenge link
Answer

3 KG

The 2 kg must be the other two thirds, so one third is 1 kg and the melon is 3 kg.

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I am a 4-digit number. My first digit is twice my last. My second digit is my first and last added together. All my digits add up to 20, and I am odd. What number am I?

Text · Genius Challenge link
Answer

6923

Call the last digit x: the digits are 2x, 3x, 20 - 6x and x. x can only be 1, 2 or 3; 1 breaks the third digit and 2 makes it even, so x = 3: 6923.

Which gem is INSIDE the loop?

Video · Medium Challenge link
Answer

A

A line from gem A to the edge crosses the wall an odd number of times; from B, C or D, an even number.

Which of the four words types the same number as BOOK?

Video · Medium Challenge link
Answer

COOK

B and C share key 2, so BOOK and COOK both type 2665.

Sun Gate to Moon Gate

Fewest days from sun to moon?

Picture · Medium Challenge link
Answer

13 DAYS

Two oases then a tower: 3 + 5 + 2 + 3 = 13.

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