He began to work a problem on a "blackboard" with a piece of chalk.

他开始用粉笔在一块“黑板”上算题。

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A great way of displaying work is to use "washing lines" across the classroom or against a wall or blackboard.

展示学生作品的一个很有用的办法是用“晾衣绳”，把绳子从教室的一头拉到另一头或把绳子钉在墙上或黑板上。

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It happens. Fortunately, while sitting in jail awaiting trial, the slow thief decided to figure what was wrong. And, amazingly enough, he had studied mathematics. And had a blackboard in the cell. So he was able to work it out.

失主叫了警察然后小偷最后被抓进了监狱,幸运的是这个贼做来牢房里,等待判决时发现了自己的错误,它很惊人的学习过数学，牢房里,还有一个黑板，它可以把题目算出来了。

麻省理工公开课 - 计算机科学及编程导论课程节选

Once connected to the system, whether inside the school or hundreds of miles away at home or work, students can log into an innovative system called Blackboard, in use now for almost three years.

CNN: Wired up for learning