a) Tính nhẩm: 200 + 800 = . . . . . 1 000 – 300 = . . . . . 300 + 10 = . . . . . 310 – 10 = . . . . . 400 + 80 + 9 = . . . . . 600 + 90 + 5 = . . . . . b) Nối phép tính với kết q

200 + 800 = 1 000

1 000 – 300 = 700

300 + 10 = 310

310 – 10 = 300

400 + 80 + 9 = 489

600 + 90 + 5 = 695

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\[\begin{array}{l} - \begin{array}{*{20}{c}}{658}\\{\underline {143} }\end{array}\\\,\,\,\,515\end{array}\]

\[\begin{array}{l} + \begin{array}{*{20}{c}}{304}\\{\underline {\,\,\,82} }\end{array}\\\,\,\,\,386\end{array}\]

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