计算:(1)0.1+0.2+0.3+0.4+…+0.9+0.1+0.11+0.12+…+0.98+0.99(2)121+12+13(1+12)×(1+13)+…+19(1+1

2024-11-15 21:36:23
推荐回答(1个)
回答1:

(1)0.1+0.2+0.3+0.4+…+0.9+0.1+0.11+0.12+…+0.98+0.99
=(0.1+0.9)×9÷2+(0.1+0.99)×90÷2
=4.5+49.05
=53.55

(2)

1
2
1+
1
2
+
1
3
(1+
1
2
)×(1+
1
3
)
+…+
1
9
(1+
1
2
)×(1+
1
3
)×…×(1+
1
9
)

=
1
2
3
2
+
1
3
3
2
×
4
3
+…+
1
9
3
2
×
4
3
×…×
10
9

=
1
2
3
2
+
1
3
4
2
+
1
4
5
2
+…+
1
9
10
2

=
1
3
+
1
6
+
1