Решебник по математике 2 класс Моро Часть 1, 2 Часть 1 | Страница 90

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\[Страница\ 90.\]

\[\boxed{\mathbf{1.}}\]

\[76 + 5 - 20 = 81 - 20 = 61\]

\[90 - 34 + 8 = 56 + 8 = 64\]

\[35 + 8 - 30 = 5 + 8 = 13\]

\[50 - 35 - 8 = 15 - 8 = 7\]

\[80 - 66 - 9 = 14 - 9 = 5\]

\[30 - 27 - 3 = 3 - 3 = 0\]

\[\boxed{\mathbf{2.}}\]

Пояснение.

Решение.

\[28 + 9 = 37\]

\[37 - 9 = 28\]

\[35 - 6 = 29\]

\[29 + 6 = 35\]

\[86 - 80 = 6\]

\[86 - 6 = 80\]

\[57 + 40 = 97\]

\[97 - 40 = 57\]

\[45 + 9 = 54\]

\[54 - 9 = 45\]

\[63 - 4 = 59\]

\[59 + 4 = 63\]

\[\boxed{\mathbf{3.}}\]

Пояснение.

Решение.

\[15 - (7 + 2) = 15 - 9 = 6\]

\[17 - (8 + 2) = 17 - 10 = 7\]

\[31 - (10 - 4 + 3) = 31 - 9 =\]

\[= 22\]

\[58 - (20 + 6) - 32 =\]

\[= 58 - 26 - 32 = 58 - 58 = 0\]

\[\boxed{\mathbf{4.}}\]

\[72 + 8 - 35 = 80 - 35 = 45\]

\[54 - 9 - 20 = 45 - 20 = 25\]

\[62 - 20 + 7 = 42 + 7 = 49\]

\[36 + 30 - 8 = 66 - 8 = 58\]

\[\boxed{\mathbf{5.}}\]

Пояснение.

Решение.

\[1)\ 15 + (20 - 10) = 15 + 10 =\]

\[= 25\]

\[2)\ 35 - (5 + 10) = 35 - 15 =\]

\[= 20\]

\[\boxed{\mathbf{6.}}\]

\[90 - 45 > 90 - 47\]

\[45 < 47\]

\[60 - 23 < 70 - 23\]

\[60 < 70\]

\[48 + 20 = 70 - 2\]

\[68 = 68\]

\[\boxed{\mathbf{7.}}\]

\[\boxed{\mathbf{8.}}\]

\[40 + 7 + 3 + 18 =\]

\[= 40 + 18 + 10 = 50 + 18 = 68\]

\[50 + 26 + 8 + 2 = 76 + 10 = 86\]

\[30 + 9 + 6 + 1 =\]

\[= 30 + 6 + 9 + 1 = 36 + 10 =\]

\[= 46\]

\[80 - (35 - 20) = 80 - 15 = 65\]

\[80 - (35 + 20) = 80 - 55 = 25\]

\[80 + (35 - 20) = 80 + 15 = 95\]

\[\boxed{\mathbf{9.}}\]

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\[5 + 10 = 15\]

\[15 - 7 = 8\]

\[8 + 4 = 12\]

\[12 - 5 = 7\]

\[7 + 4 = 11\]

\[11 - 6 = 5\]

\[5 + 5 = 10\]