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BEBRAS 2021 Grade 9-10 Round 2 Ext Question 14

BEBRAS · BEBRAS 2021 Grade 9-10 Round 2 Ext

Question 14

Sam builds towers from equal-height blocks. Every block within one tower has the same width. He may add or remove blocks to make all towers equally high. Adding or removing one block costs its width in change units; for example two width 1 removals cost 2, and four width 3 additions cost 12.

Question illustration

What is the smallest total change?
  1. 27
  2. 35
  3. 39
  4. 42