①3.6-2.8+7.4-7.2
=(3.6+7.4)-(2.8+7.2)
=11-10
=1
②
÷23+8 17
×1 23
+9 17
1 23
=
×8 17
+1 23
×1 23
+9 17
1 23
=(
+8 17
+1)×9 17
1 23
=2×
1 23
=
2 23
③88×1.01
=88×(1+0.01)
=88×1+88×0.01
=88+0.88
=88.88
④45÷[(13+25 )×411]
=45÷(38×411)
=45÷15618
=
15 5206
⑤(
+1 2
)÷1 3
-3 5
17 18
=
×5 6
-5 3
17 18
=
-25 18
17 18
=
8 18
=
4 9
⑥49×102
=49×(100+2)
=49×100+49×2
=4900+98
=4998