AMO 2017 — Primary 5 (Grade 5) Question 3

Find the value of 10 × 1 − 9 × 2 + 8 × 3 − 7 × 4 + 6 × 5 − 5 × 6 + 4 × 7 − 3 × 8 + 2 × 9 − 1 × 10.