计算:2+4+6+8+10+12+14+16

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计算:2+4+6+8+10+12+14+16+18

参考答案:

2+4+6+8+10+12+14+16+18

=(2+18)+(4+16)+(6+14) +(8+12)+10

=20+20+20+20+10

=90