358 · 90 = (358 · 9) · 10 Выполните умножение, используя удобные способы записи. 516 · 50 274 · 80 407 · 30 140 · 20 920 · 80 570 · 70 209 · 40 960 · 96 210 · 80 Вычислите устно. 600 · 10 500 · 90 70 · 40 200 · 50 400 · 50 300 · 30

Выполним умножение, используя удобные способы записи:

1. 516 × 50 = 516 × 5 × 10 = (500 + 16) × 5 × 10 = (500 × 5 + 16 × 5) × 10 = (2500 + 80) × 10 = 2580 × 10 = 25800
2. 274 × 80 = 274 × 8 × 10 = (200 + 74) × 8 × 10 = (200 × 8 + 74 × 8) × 10 = (1600 + 592) × 10 = 2192 × 10 = 21920
3. 407 × 30 = 407 × 3 × 10 = (400 + 7) × 3 × 10 = (400 × 3 + 7 × 3) × 10 = (1200 + 21) × 10 = 1221 × 10 = 12210
4. 140 × 20 = 14 × 10 × 2 × 10 = 14 × 2 × 100 = 28 × 100 = 2800
5. 920 × 80 = 92 × 10 × 8 × 10 = 92 × 8 × 100 = 736 × 100 = 73600
6. 570 × 70 = 57 × 10 × 7 × 10 = 57 × 7 × 100 = 399 × 100 = 39900
7. 209 × 40 = 209 × 4 × 10 = (200 + 9) × 4 × 10 = (200 × 4 + 9 × 4) × 10 = (800 + 36) × 10 = 836 × 10 = 8360
8. 960 × 96 = (1000 - 40) × 96 = 1000 × 96 - 40 × 96 = 96000 - 3840 = 92160
9. 210 × 80 = 21 × 10 × 8 × 10 = 21 × 8 × 100 = 168 × 100 = 16800

Вычислим устно:

1. 600 × 10 = 6000
2. 500 × 90 = 45000
3. 70 × 40 = 2800
4. 200 × 50 = 10000
5. 400 × 50 = 20000
6. 300 × 30 = 9000

Ответ: 25800, 21920, 12210, 2800, 73600, 39900, 8360, 92160, 16800, 6000, 45000, 2800, 10000, 20000, 9000