减法的性质
639-85-15
639-85-15
例:
639-85-15
273-(173-18)
试一试:
47-32+22 47-(32-22)
=15+22
=37
47-32+22=47-(32-22)
=47-10
=37
26-(16-4)
=26-12
=14
26-16+4
=10+4
=14
26-(16-4)=26-16+4
454-155+45=454-( )155-45
454-155-45=454-( )155+45
78-(28-15)=78
78-(28+15)=78
-28+15
-28-15
11+9-3 =11
14+(16-5)=14
+(9-3)
+16-5
填一填
189-53+23=
189+53+47=
514+(36-19)=
435-(235-19)=
189-(53-23)
189+(53+47)
514+36-19
435-235+19
2847-(847+629)=
753-463-153=
38-(15+18)=
456+78-56=
填一填
用简便方法计算
265-37-63
172-(72+85)
96-(46-13)
239+85-15
241+(59-27)
803-132-168
下面各题哪些能用简便方法计算?
① 147-76-24 ② 425-263-63
③ 147-26+74 ④ 96-(18+26)
⑤ 93+24+7 ⑥ 54+39-29
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