Упр.91 Часть 1 ГДЗ Рабочая тетрадь Истомина 4 класс (Математика)

а)

$$59 \cdot 7 = 413$$
$$59 \cdot 270 = 59 \cdot 27 \cdot 10 = 1593 \cdot 10 = 15930$$
$$20 \cdot 59 = 2 \cdot 59 \cdot 10 = 118 \cdot 10 = 1180$$
$$159300 : 27 = 1593 : 27 \cdot 100 = 59 \cdot 100 = 5900$$
$$413 + 1180 = 1593$$
$$1593 — 413 = 1180$$
$$590 \cdot 7 = 59 \cdot 7 \cdot 10 = 413 \cdot 10 = 4130$$
$$59 \cdot 20 = 59 \cdot 2 \cdot 10 = 118 \cdot 10 = 1180$$

б)

$$415 \cdot 60 = 415 \cdot 6 \cdot 10 = 2490 \cdot 10 = 24900$$
$$416 \cdot 36 = (415 + 1) \cdot 36 = 14940 + 36 = 14976$$
$$300 \cdot 415 = 3 \cdot 415 \cdot 100 = 1245 \cdot 100 = 124500$$
$$14940 : 415 = 36$$
$$1494 — 249 = 1245$$
$$149400 : 36 = 14940 : 36 \cdot 10 = 415 \cdot 10 = 4150$$
$$415 \cdot 30 = 415 \cdot 3 \cdot 10 = 1245 \cdot 10 = 12450$$
$$415 \cdot 37 = 415 \cdot (36 + 1) = 14940 + 415 = 15355$$

в)

$$2149 \cdot 70 = 2149 \cdot 7 \cdot 10 = 15043 \cdot 10 = 150430$$
$$152579 — 150430 = 2149$$
$$2149 \cdot 7 = 15043$$
$$2149 \cdot 71 = 2149 \cdot (70 + 1) = 150430 + 2149 = 152579$$
$$152579 — 2149 = 150430$$
$$2149 + 150430 = 152579$$