✔ 最佳答案
28到661數字中,奇數和偶數和相差多少?
Sol
(29+31+33+…+661)-(28+30+32+…+660)
28+30+32+…+660
=(28+660)*[(660-28)/2+1]/2
=688*317/2
=109048
29+31+33+…+661
=(29+661)*[(661-29)/2+1]/2
=690*317/2
=109365
109365-109048=317
or
(29+31+33+…+661)-(28+30+32+…+660)
=(29-28)+(31-30)+(33-32)+…+(661-660)
=1+1+1+…+1
=(661-29)/2+1
=317