Sat数学题求解释和过程
Atadepartmentstore,3/5oftheitemsarediscountedby50percent,1/5oftheitemsarediscountedby70percent,1/10oftheitemsarediscountedby80percent,andallotheritemsarenotdiscounted.Ifoneitemistobechosenatrandom,whatisthepropabilitythattheitemisdiscountedbyeither50percentor70percent?
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