一种混凝土是由水泥、黄沙、石子按2:3:5的比例配制而成的,现在工地上有水泥10吨、黄沙18吨、石子28吨,谁最先用完,要想把所有材料都用完,还要再购进什么?购进多少吨?
快点啊
如果好····················································200悬赏分极限!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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