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🔢 быстрые приемы сложения и вычитания #реальнаяматематикаPLUS #математика


less than 1m read
·Nov 3, 2024

9.990 и, допустим, там 4.250. Сами понимаете, что складывать их в уме не очень удобно, потому что там всякие переходы через десяток, которые могут запутать.

Возьмём близкое к нему число 10.000. К 10.000 прибавить 4.250 несложно: 14.2. В конце мы эти 10 обратно вычтем и получим не 14.50, а 14.20.

Кстати, эту же идею можно оформить чуть иначе: просто 10 перебросить из второго слагаемого в первое, и тогда мы получим первое 10.000, а второе 4.240.

Попробуем сделать похожую вещь только с вычитанием. Вот сделаем 4.999, и теперь вычитать будет легко: 3765.

Но у нас было на один больше. Ну так давайте этот один вернём, и, собственно, получим 3766. Это и есть окончательный ответ.

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