2+31/6+51/12+71/20+111/30+131/42=_.
问题描述:
2+3
+51 6
+71 12
+111 20
+131 30
=______. 1 42
答
2+3
+51 6
+71 12
+111 20
+131 30
1 42
=(2+3+5+7+11+13)+
+1 6
+1 12
+1 20
+1 30
1 42
=41+
-1 2
+1 3
-1 3
+1 4
-1 4
+1 5
-1 5
+1 6
-1 6
1 7
=41+
-1 2
1 7
=41
.5 14
故答案为:41
.5 14