选择合理的方法计算下列各题.
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选择合理的方法计算下列各题.
①517+1905÷15-629;
②4
①517+1905÷15-629;
②4
3 |
5 |
①517+1905÷15-629
=517+127-629
=644-629
=15
②4
3
5-1.25-0.75+0.4
=4.6-1.25-0.75+0.4
=(4.6+0.4)-(1.25+0.75)
=5-2
=3
③4.75×
2
5+5.25÷2.5
=4.75×
2
5+5.25÷
5
2
=4.75×
2
5+5.25×
2
5
=(4.75+5.25)×
2
5
=10×
2
5
=4
④(
5
7-
2
3)÷
5
21×5
=(
5
7-
2
3)×(
21
5×5)
=(
5
7-
2
3)×21
=
5
7×21-
2
3×21
=15-14
=1
=517+127-629
=644-629
=15
②4
3
5-1.25-0.75+0.4
=4.6-1.25-0.75+0.4
=(4.6+0.4)-(1.25+0.75)
=5-2
=3
③4.75×
2
5+5.25÷2.5
=4.75×
2
5+5.25÷
5
2
=4.75×
2
5+5.25×
2
5
=(4.75+5.25)×
2
5
=10×
2
5
=4
④(
5
7-
2
3)÷
5
21×5
=(
5
7-
2
3)×(
21
5×5)
=(
5
7-
2
3)×21
=
5
7×21-
2
3×21
=15-14
=1