脱式计算.(能简算的要简算) ①1÷0.25+0.25÷1-2.5×0.1 ②1+2+3+4+5+6+5+4+3+2+1/6666662 ③2/2×4+2/4×6+2/6×8+2/8×10+2/10×12 ④1÷(1-0.99)-99÷(1

问题描述:

脱式计算.(能简算的要简算)
①1÷0.25+0.25÷1-2.5×0.1

1+2+3+4+5+6+5+4+3+2+1
6666662

2
2×4
+
2
4×6
+
2
6×8
+
2
8×10
+
2
10×12

④1÷(1-0.99)-99÷(1-0.999)

①1÷0.25+0.25÷1-2.5×0.1,
=4+0.25-0.25,
=4+(0.25-0.25),
=4+0,
=4;

1+2+3+4+5+6+5+4+3+2+1
6666662

=
36
6666662

=
18×2
3333331×2

=
18
3333331

2
2×4
+
2
4×6
+
2
6×8
+
2
8×10
+
2
10×12

=
1
2
-
1
4
+
1
4
-
1
6
+
1
6
-
1
8
+
1
8
-
1
10
+
1
10
-
1
12

=
1
2
-
1
12

=
5
12

④1÷(1-0.99)-99÷(1-0.999),
=1÷0.01-99÷0.001,
=100-99000,
=-98900.