An amulet spells ABRACADABRA in a pyramid of letters — how many ways can you trace it?
A charm against fever arranges the letters of ABRACADABRA in a triangular pyramid, one new letter added per row, so the word can be spelled out by moving from the top letter down to an adjoining letter in each row below. In how many different ways can the word be traced from top to bottom?
Reveal the answer
1,024 ways. ABRACADABRA has 11 letters, so there are 10 steps down the pyramid, and at each step you can move to one of two adjoining letters — giving 2 to the power of 10. From Henry Dudeney's The Canterbury Puzzles (1907), where it appears as a charm against ague.
— Henry Dudeney, The Canterbury Puzzles — 1907, 'The Amulet'