2. Вычислите значения произведений, используя распределительное свойство умножения: а) 81 ⋅ 5; б) 408 ⋅ 7; в) 397 ⋅ 4; г) 298 ⋅ 4.

а) \(81 ⋅ 5 = (80 + 1) ⋅ 5 = 80 ⋅ 5 + 1 ⋅ 5 = 400 + 5 = 405\).

б) \(408 ⋅ 7 = (400 + 8) ⋅ 7 = 400 ⋅ 7 + 8 ⋅ 7 = 2800 + 56 = 2856\).

в) \(397 ⋅ 4 = (400 − 3) ⋅ 4 = 400 ⋅ 4 − 3 ⋅ 4 = 1600 − 12 = 1588\).

г) \(298 ⋅ 4 = (300 − 2) ⋅ 4 = 300 ⋅ 4 − 2 ⋅ 4 = 1200 − 8 = 1192\).

Ответ: а) 405; б) 2856; в) 1588; г) 1192.