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Australian AMC 2017 - Upper Primary Question 9

AMC AUSTRALIA · Australian AMC 2017 - Upper Primary

Question 9

Felicity has a combination lock for her bike like the one shown. Each tumbler has the numbers 0 to 9. It clicks whenever a tumbler moves one number forward or back, including between 9 and 0. The lock starts at 9–0–4; her combination is 5–8–7. What is the least number of clicks needed?

Question illustration
  1. 20
  2. 18
  3. 17
  4. 9
  5. 7