1)405 × 82 + 405 × 18 = 405 × (82 + 18) = 405 × 100 = 40500
2)497 × 38 - 496 × 38 = (497 - 496) × 38 = 38
1)
405 × 82 + 405 × 18 = 405 × (82 + 18) = 405 × 100 = 40500
2)
497 × 38 - 496 × 38 = (497 - 496) × 38 = 38