3. Вычислите удобным способом: а) 121 ⋅ 5; б) 34 ⋅ 101; в) 211 ⋅ 5; г) 79 ⋅ 9; д) 89 ⋅ 6; е) 312 ⋅ 8.

а) \(121 ⋅ 5 = 120 ⋅ 5 + 1 ⋅ 5 = 600 + 5 = 605\).

б) \(34 ⋅ 101 = 34 ⋅ (100 + 1) = 3400 + 34 = 3434\).

в) \(211 ⋅ 5 = 210 ⋅ 5 + 1 ⋅ 5 = 1050 + 5 = 1055\).

г) \(79 ⋅ 9 = (80 − 1) ⋅ 9 = 720 − 9 = 711\).

д) \(89 ⋅ 6 = (90 − 1) ⋅ 6 = 540 − 6 = 534\).

е) \(312 ⋅ 8 = (300 + 12) ⋅ 8 = 2400 + 96 = 2496\).

Ответ: а) 605; б) 3434; в) 1055; г) 711; д) 534; е) 2496.