选用恰当的方法计算下列各题：（1）59×[57-（1720-27）]（2）7.81×0.1+0.5×78.1+0.049×781（3）1.15
选用恰当的方法计算下列各题：（1）59×[57-（1720-27）]（2）7.81×0.1+0.5×78.1+0.049×781（3）1.15÷[110×（9.75-4....
选用恰当的方法计算下列各题：（1）59×[57-（1720-27）]（2）7.81×0.1+0.5×78.1+0.049×781（3）1.15÷[110×（9.75-4.25）]（4）1281116×135+71516×35．
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展开全部
（1）
×[
-（
-
）]
=
×[
-
+
]
=
×[
+
-
]
=
×[1-
]
=
×
=
；
（2）7.81×0.1+0.5×78.1+0.049×781
=7.81×0.1+5×7.81+4.9×7.81
=7.81×（0.1+5+4.9）
=7.81×10
=78.1；
（3）1.15÷[
×（9.75-4.25）]
=1.15÷[
×5.5]
=1.15÷0.55
=
；
（4）128
×1
+71
×
=128
×（1+
）+71
×
=128
×1+128
×
+71
×
=128
+（128
+71
）×
=128
+200×
=128
+120
=248
．
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| 5 |
| 7 |
| 17 |
| 20 |
| 2 |
| 7 |
=
| 5 |
| 9 |
| 5 |
| 7 |
| 17 |
| 20 |
| 2 |
| 7 |
=
| 5 |
| 9 |
| 5 |
| 7 |
| 2 |
| 7 |
| 17 |
| 20 |
=
| 5 |
| 9 |
| 17 |
| 20 |
=
| 5 |
| 9 |
| 3 |
| 20 |
=
| 1 |
| 12 |
（2）7.81×0.1+0.5×78.1+0.049×781
=7.81×0.1+5×7.81+4.9×7.81
=7.81×（0.1+5+4.9）
=7.81×10
=78.1；
（3）1.15÷[
| 1 |
| 10 |
=1.15÷[
| 1 |
| 10 |
=1.15÷0.55
=
| 23 |
| 11 |
（4）128
| 11 |
| 16 |
| 3 |
| 5 |
| 5 |
| 16 |
| 3 |
| 5 |
=128
| 11 |
| 16 |
| 3 |
| 5 |
| 5 |
| 16 |
| 3 |
| 5 |
=128
| 11 |
| 16 |
| 11 |
| 16 |
| 3 |
| 5 |
| 5 |
| 16 |
| 3 |
| 5 |
=128
| 11 |
| 16 |
| 11 |
| 16 |
| 5 |
| 16 |
| 3 |
| 5 |
=128
| 11 |
| 16 |
| 3 |
| 5 |
=128
| 11 |
| 16 |
=248
| 11 |
| 16 |
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