1.计算:13 14 15 16 17 25
2.计算:2 3 4 5 15 16 17 18 20
3.计算:21 22 23 24 25 26 27 28 29
4.计算:5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
5.计算:22-20 18-16 14-12 10-8 6-4 2-0
6.计算:10-20 30-40 50-60 70-80 90
7.计算:(2 4 6 8 10)-(1 3 5 7 9)
8.计算:(2 4 6 … 20)-(1 3 5 … 19)
9.计算:(2 4 6 … 100)-(1 3 5 … 99)
答案:
1.解:见下图:
2.解:见下图:
3.解:见下图:
4.解:
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
=1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20-(1 2 3 4)
=210-10
=200
5.解:
22-20 18-16 14-12 10-8 6-4 2-0
=(22-20) (18-16) (14-12) (10-8) (6-4) (2-0)
=2 2 2 2 2 2
=12
6.解:
10-20 30-40 50-60 70-80 90
=10 30-20 50-40 70-60 90-80
=10 (30-20) (50-40) (70-60) (90-80)
=10 10 10 10 10
=50
7.解:
(2 4 6 8 10)-(1 3 5 7 9)
=(2-1) (4-3) (6-5) (8-7) (10-9)
=1 1 1 1 1
=5
8.解:
(2 4 6 … 20)-(1 3 5 … 19)
9.解:
(2 4 6 … 100)-(1 3 5 … 99)