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BEBRAS 2026 Grade 3-4 Round 2 Ext Question 11

BEBRAS · BEBRAS 2026 Grade 3-4 Round 2 Ext

Question 11

Bob has four tubes, each holding at most two round sweets. The first three are full and the fourth is empty. Colours are blue (X), red (Đ), yellow (V); the source uses letters on grey circles. Bob wants each colour grouped in its own tube.

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A move D(i-j) transfers the top sweet of tube i to tube j, which must have space. These two independent examples explain D(1-2) and D(3-4).

Question illustration



Question illustration

Which move sequence sorts the original sweets?
  1. D(1-4), D(3-1), D(3-4), D(2-3)
  2. D(3-4), D(2-4), D(1-3), D(1-2)
  3. D(2-4), D(3-2), D(1-3), D(1-4)
  4. D(2-4), D(1-2), D(3-1), D(1-4)