1.3/7 × 49/9 - 4/3 2.8/9 × 15/36 + 1/27 3.12× 5/6 – 2/9 ×3 4.8× 5/4 + 1/4 5.6÷ 3/8 – 3/8 ÷6 6.4/7 × 5/9 + 3/7 × 5/9 7.5/2 -（ 3/2 + 4/5 ） 8.7/8 + （ 1/8 + 1/9 ） 9.9 × 5/6 + 5/6 10.3/4 × 8/9 - 1/3 11.7 × 5/49 + 3/14 12.6 ×（ 1/2 + 2/3 ） 13.8 × 4/5 + 8 × 11/5 14.31 × 5/6 – 5/6 15.9/7 - （ 2/7 – 10/21 ） 16.5/9 × 18 – 14 × 2/7 17.4/5 × 25/16 + 2/3 × 3/4 18.14 × 8/7 – 5/6 × 12/15 19.17/32 – 3/4 × 9/24 20.3 × 2/9 + 1/3 1、 7.5*3.1/2.5*100 =7.5/2.5*3.1*100 =3*3100 =9300 2、36.5*6.2+28*0.365+3.65 =36.5*6.2+2.8*3.65+3.65 =3.65*（6.2+2.8+1） =3.65*1.=36.5 3、999.9*599.9+199.9 =1000×599+0.1×599.9+200-0.1 =5990+59.9+200-0.1 =6049.9+200-0.1 =6249.9-0.1 =6249.8 999.9*599.9+199.9 =(1000-0.1)*599.9+(200-0.1) =1000*599.9-0.1*599.9+200-0.1 =599900-599.99+200-0.1 =599900-(600-0.1)+200-0.1 =599900-600+0.1+200-0.1 =599900-600+200 =599500 999.9X599.9+199.9 =(1000-0.1)X599.9+(200-0.1) =1000X599.9-0.1X599.9+200-0.1 =599900-59.99+200-0.1 =599900-(60-0.01)+200-0.1 =599900-60+0.01+200-0.1 =599900+200+0.01-60-0.1 =600039.91 999.9×599.9+199.9 =（1000－0．1）×599.9+199.9 ＝1000×599.9－0.1×599.9+199.9 ＝599900－59.9+199.9 ＝599900＋140 ＝60040