I . 1). 2； 9 2) 16/ 15; 5/9 3) 1/4; 3.25 4)35/6; 4 3/8; 5) 10/9 6)3/4; 5/6; 2/5; 8/3; 10/ 1 1 7) 14/ 15; 1/4; 6:2: 1 8) 18 9)8 10)> 1 1) 1/52 12) 12

13) 1/4 14)2π/3 15)2/3 16)55/72,59/72,6 1/72 17)7.5 18)2. 1

Second, D B C.

Three. 1)3/25×5/8×5/8=3/64

2) 16/3÷{(5/3+ 1/5)× 15/7}= 16/3÷{28/ 15× 15/7}= 16/3÷4=4/3

3) 5/6: 5 =1/6:1=1:6 = 4: 24, so x=24.

4) 1/4: 1/3 (both sides of the ratio are multiplied by 12 at the same time, and the ratio remains unchanged) = 3: 4 = 3/4:1= a: b.

b:c=3:4= 1:4/3

Say A: B: C = 3/4: 1: 4/3 (all items are multiplied by12) = 9:12:16.

4. 1) You don't want to learn the index, just calculate it for one month at a time.

The first month is10000× (1+0.14% (1-20%)) =1001.2.

The second month is10011.2× (1+0.14% (1-20%)) =10022.4.

The third month is10022.4× (1+0.14% (1-20%)) =10033.6.

Xiaoming's father got 10033.6 yuan.

2)①2000×0.9= 1800 (yuan)

②1800 ÷ (1+50%) =1200 (yuan)

③(2000- 1200)÷ 1200× 100%=66.7%

It's hard to write, so LZ will give more points.