close
4004
一題數學問題~~~~~來看看唷!
For the four-digit integers (from 1000 to 9999) how many are palindromsand what is their sum?
there are1001
1111
1221
...
1991
2002
2112
...
2992
3003
...
3993
4004
...
4994
5005
...
5995
6006
...
6996
7007
...
7997
8008
...
8998
9009
...9999
so the four-digit integers have 10 10 ... 10=10*9=90
and their sum is [(1001 1991)*10/2] [(2002 2992)*10/2] ... [(9009 9999)*10/2=(2992 4994 6996 ... 19008)*5= 495000
大大您這是大學微積分原文書的題目嗎？
離散數學的＠＠
文章標籤
全站熱搜
留言列表
