work on 与work at 可通用,表示“忙于……”。但在work on sth. 中,sth是work的具体对象;而在work at sth. 中,sth. 只说明所从事工作的性质,即时间、精力用在某一方面的事情上,而不在于说明正在做什么。如:He is working on/ at a novel. 他正在专心写一部小说。They have worked at this subject for many years. 他们从事这项课题的研究已经好多年了。Bob worked hard on organizing other singers to sing for him for free.鲍勃积极地组织其他歌唱家为他义务演唱。work out 算出;解决①Can you work out how much money it will need? 你能算出需多少钱吗?②Ive worked out the problem. 我已解决了这个问题。work in 和work at都是在某处工作例句:he work in/at a factory他在一个工厂工作work on 研究某方面的东西例句:he is work on this project他在研究这个项目