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SEAMO 2022 — Paper A — Grade 1–2 Question 9

SEAMO · SEAMO 2022 — Paper A — Grade 1–2

Question 9

Evaluate $1-2+3-4+5-6+\cdots-20+21$.
  1. $11$
  2. $13$
  3. $15$
  4. $17$
  5. $21$