小三數學題一條

{(1+99)*99} / 2
= 4950

頭加尾乘項數除二

I thing it's~4950

(1+99)x99/2
=4950

100x2/2
=4950

2007-05-22 19:01:17 補充：
100x99/2=4950

2007-05-22 19:01:49 補充：
100x99/2=4950

將佢當成個梯形,

梯形面積係:(上底+下底)x高/2

咁呢題數既上底就係1,下底係99

因為你要加99個數,

所以高就係99

算式就係:

(1+99)x99/2

=100x99/2

=4950

答:4950

1+2+3+......+98+99 =17701

= [(1+99)/2] *99
= 4950


*第1個數加最尾果個數,再除2, 再乘以項數

其實計呢條數係有口訣GE 就係：首項加尾項 乘項數 除二

所以

1+2+3+...+98+99

= (1+99)x99/2

= 4950

= [(1+99)/2] *99
= 4950


*頭加尾除以2, 再乘以項數*

no. 1= 4950