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Riddles, one at a time

At which step number are all three gems at the top again?

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Answer

36 STEPS

Notches 9, 6 and 4: the first common multiple is 36.

After how many hours are they the same height?

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Answer

5 hours

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

Stack the Stones

Which number belongs on the top brick?

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Answer

44

20 - 9 = 11, 13 + 11 = 24, then 24 + 20 = 44.

Moving only right or up, how many different routes lead from start to the gem?

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Answer

8

There are 20 routes in all, and 12 of them pass the cone: 20 − 12 = 8.

Move exactly one rod. What is the true equation?

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Answer

9 − 8 = 1

The top rod of the 7 turns the 3 into a 9.

Lemon, Tea and Dates

What is the answer to the last line?

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Answer

25

Lemon 10, cup 5, date 2. Multiply first: 5 + 20 = 25.

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