1. 想一想先算什么、后算什么,再计算。
$21 + 39 - 40 = $ $28 + 16 ÷ 4 = $ $70 - 28 + 4 = $
$30 - 16 ÷ 2 = $ $63 ÷ 9 + 47 = $ $34 + 18 ÷ 2 = $
$24 + 26 - 25 = $ $44 + 8 × 7 = $ $36 ÷ (51 - 45) = $
$21 + 39 - 40 = $ $28 + 16 ÷ 4 = $ $70 - 28 + 4 = $
$30 - 16 ÷ 2 = $ $63 ÷ 9 + 47 = $ $34 + 18 ÷ 2 = $
$24 + 26 - 25 = $ $44 + 8 × 7 = $ $36 ÷ (51 - 45) = $
答案:
20 32 46 22 54 43 25 100 6
2. 比一比,算一算。
$\left\{\begin{array}{l} 4 + 2 × 8 = \\ (4 + 2) × 8 = \end{array}\right.$ $\left\{\begin{array}{l} 63 - 21 ÷ 7 = \\ (63 - 21) ÷ 7 = \end{array}\right.$ $\left\{\begin{array}{l} 48 ÷ 6 + 2 = \\ 48 ÷ (6 + 2) = \end{array}\right.$
$\left\{\begin{array}{l} 4 + 2 × 8 = \\ (4 + 2) × 8 = \end{array}\right.$ $\left\{\begin{array}{l} 63 - 21 ÷ 7 = \\ (63 - 21) ÷ 7 = \end{array}\right.$ $\left\{\begin{array}{l} 48 ÷ 6 + 2 = \\ 48 ÷ (6 + 2) = \end{array}\right.$
答案:
20 60 10 48 6 6
3. 下面的计算对吗?把不对的改正过来。
$6 × 9 - 5$ $3 × 6 ÷ 9$ $(3 + 5) × 6$
$= 6 × 4$ $= 18 ÷ 9$ $= 3 + 30$
$= 24$ $= 2$ $= 33$
$6 × 9 - 5$ $3 × 6 ÷ 9$ $(3 + 5) × 6$
$= 6 × 4$ $= 18 ÷ 9$ $= 3 + 30$
$= 24$ $= 2$ $= 33$
答案:
$ 6 \times 9 - 5 $ $ (3 + 5) \times 6 $
$ = 54 - 5 $ $ = 8 \times 6 $
$ = 49 $ $ = 48 $
$ = 54 - 5 $ $ = 8 \times 6 $
$ = 49 $ $ = 48 $
4. 请把两个算式合并成一个综合算式。
$\left\{\begin{array}{l} 27 + 14 = 41 \\ 41 + 26 = 67 \end{array}\right.$ $\left\{\begin{array}{l} 4 × 6 = 24 \\ 28 + 24 = 52 \end{array}\right.$ $\left\{\begin{array}{l} 20 - 5 = 15 \\ 30 - 15 = 15 \end{array}\right.$
______ ______ ______
$\left\{\begin{array}{l} 27 + 14 = 41 \\ 41 + 26 = 67 \end{array}\right.$ $\left\{\begin{array}{l} 4 × 6 = 24 \\ 28 + 24 = 52 \end{array}\right.$ $\left\{\begin{array}{l} 20 - 5 = 15 \\ 30 - 15 = 15 \end{array}\right.$
______ ______ ______
答案:
$ 27 + 14 + 26 = 67 $ $ 28 + 4 \times 6 = 52 $ $ 30 - (20 - 5) = 15 $
5. 看图读数、写数。

答案:
二千零三十二 一千零一十 四百零六 2032 1010 406
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