21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40=?

来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/25 10:51:12
21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40=?21+22+23+24+25+26+27+28+29+30+31+32+33+

21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40=?
21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40=?

21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40=?
=(21+40)+(22+39)+……+(30+31)
=61+61+……+61
=61×10
=610

610

一共20个数,首尾相加均得61,如21加40,22加39,一共十组数字,故得610

共20个数,则答案为20*(21+40)/2=610

610