1＋2````````````````````````````＋100000000
＝（1+100000000）*100000000/2
=5000000050000000
这种类似的题目有公式可以用
和=（首项+末项）×项数/2
这里的首项就是1,末项和项数都是100000000
1＋2````````````````````````````＋100000000＝?
1＋2````````````````````````````＋100000000
＝（1+100000000）*100000000/2
=5000000050000000
这种类似的题目有公式可以用
和=（首项+末项）×项数/2
这里的首项就是1,末项和项数都是100000000