5+6+7+8+9+10........+111 = ?

=(1+2+3+4+5......+111)-(1+2+3+4)
=(1+111)*111/2-(1+4)*4/2
=56*111-5*2
=6216-10
=6116

2006-10-21 14:36:02 補充：
6216-10=6206sorry!

5+6+7+8+9+10........+111
=(5+111)x107/2 ←(頭項+尾項x項數)/2
=6206

(5+111)*(111-4)
———————
2
=116*107
————
2
=58*107
=6206

公式：(頭項+尾項)*項數/2

1+2+3+4+........+100=5050
111-100=11
1+2+3+4=10
11-10=1
5050+1=5051 lo...
我都不知對不對家!

2006-10-21 10:18:37 補充：
有錯1+2+3+4+........+100=5050101+ 102+ 103+ 104.........+ 111=11661+ 2+ 3+ 4=101166-10 =11565050+ 1156=6206 !!!!!!!!!!!!!!!!!這個絕對正確 !!!!!!!!!

111-5=53
(111+5)*53
=6148

2006-10-20 23:01:58 補充：
111-5=106106/2=53(111+5)*53=6148

[(5+111)x(111-1-2-3-4)]/2
=5858

2006-10-20 23:06:32 補充：
sorryI forget somethingthe real sum is: [(5 111)x(111-5)]/2=[116x106]/2=12296/2=6148

5+6+7+8+9+10........+111

=(5+111)x107/2

=6206

你可以試下
(首項 + 末項) x 項數 / 2
= (5 + 111) x ( 111 - 5 ) / 2
= ( 116 ) x ( 106 ) / 2
= 6148

2006-10-20 22:42:39 補充：
sori我計錯左項數項數 = 111 - 4 = 107so the answer is(首項 末項) x 項數 / 2= (5 111) x ( 111 - 4 ) / 2= ( 116 ) x ( 107 ) / 2= 6206

You can your teacher ?...or read Maths book?

2006-10-20 22:36:15 補充：
Am I right...!!! 相信我 ...

[111*(111+1)]/ 2 - [4*(4+1) ]/ 2

=6216-10

=6206