=38/5-12+6/5-4.9+9/4-4.1-2.25
=7.6-12+1.2-4.9+2.25-4.1-2.25
=-12.2
答案:-10,你把2.25换成2又1/4,或者2又1/4换成2.25就好算了。
7又3/5-12+3又2/5+(-4.9)-(-2又1/4)-4.1-2.25
(遇到分数小数混合运算,先化成同一种形式,此题化成小数简单易运算)
=7.6-12+3.4+(-4.9)
+2.25-4.1-2.25
=7.6-12+3.4-4.9+2.25-4.1
-2.25
(观察结合凑整数)
=7.6+3.4-(4.9+4.1)+2.25-2.25-12
=11-9-12
=-10
7又3/5-12+3又2/5+(-4.9)-(-2又1/4)-4.1-2.25
=7.6-12+3.4-4.9+2.25-4.1-2.25
=(7.6+3.4)-12-(4.9+4.1)+(2.25-2.25)
=11-12-9+0
=-10
即原题等于-10。