Question

直接寫出得數(shù) 5 28 ×7=	4 5 × 4 7 =	5- 3 7 =	7 24 × 3 14 =	1 6 + 5 6 × 1 5 =
20×4%=	0.36+1.42=	3.8-2.07=	657-598=	398×59≈

Answer 1

分析：①④約分計(jì)算；②分子相乘的積做分子，分母相乘的積做分母；③把5化成分母為7的分?jǐn)?shù)，在相減；⑤先算乘法，再算加法；⑥把4%化成小數(shù)計(jì)算；⑦⑧注意小數(shù)點(diǎn)對(duì)齊；⑨注意數(shù)位對(duì)齊；⑩估算時(shí)，把398看作400，把59看作60．

解答：解：

5

28

×7=

5

4

；      

4

5

×

4

7

=

16

35

；           5-

3

7

=4

4

7

；        

7

24

×

3

14

=

1

16

；         

1

6

+

5

6

×

1

5

=

1

3

；
20×4%=0.8；         0.36+1.42=1.78；      3.8-2.07=1.73；     657-598=59；           398×59≈24000；

點(diǎn)評(píng)：此題考查了約分、運(yùn)算順序、數(shù)字轉(zhuǎn)化以及估算的方法．