小陈从广州开直升飞机去上海看世博，去时很兴奋，开的很快，速度为150千米／时，回时很累，开的很慢，速度只有100小陈从广州开直升飞机去上海看世博，去时很兴奋，开的很快，速度为150千米/时，回时很累，开的很慢，速度只有100千米/时，问：小胡往返广州和上海的平均速度是______．

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