问题
填空题
计算: (1)125×888=______. (2)1
|
答案
解(1)125×888=,
=(125×8)×111,
=1000×111,
=111000;
(2)1
+31 2
+51 6
+71 12
+91 20
,1 30
=(1+3+5+7+9)+
+1 2
+1 6
+1 12
+1 20
,1 30
=25+
+1 2
-1 2
+1 3
-1 3
+1 4
-1 4
+1 5
-1 5
,1 6
=25+1-
,1 6
=25
;5 6
故答案为:11100,25
.5 6