计算:1+31/6+51/12+71/20+91/30+111/42+131/56+151/72+171/90.
问题描述:
计算:1+3
+51 6
+71 12
+91 20
+111 30
+131 42
+151 56
+171 72
. 1 90
答
1+3
+51 6
+71 12
+91 20
+111 30
+131 42
+151 56
+171 72
,1 90
=1+(3+
)+(5+1 6
)+(7+1 12
)+(9+1 20
)+(11+1 30
)+(13+1 42
)+(15+1 56
)+(17+1 72
),1 90
=(1+3+5+7+9+11+13+15+17)+(
+1 6
+1 12
+1 20
+1 30
+1 42
+1 56
+1 72
),1 90
=81+
,2 5
=81
.2 5