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VTMO 2013 — Grade 7 — semifinal Question 6

VTMO · VTMO 2013 — Grade 7 — semifinal

Question 6

For every integer $30$ through $50$, subtract the units digit from the tens digit. Sum all results.
  1. $0$
  2. $- 5$
  3. $5$
  4. $- 15$
  5. $15$