31. This model of typewriter is efficient and durable, economical and practical for middle school students.

这个型号的打字机对中学生来说，高效、耐用、经济、实惠。

32. The computer we produced is characterized by its high quality, compact size, energy saving and is also easy to learn and easy to operate.

我们生产的计算机其特点是质量好，体积小，节能，而且易学好用。

33. They are not only as low-priced as the goods of other markers, but they are distinctly superior in the following respects.

它们不但和其它厂家的产品一样低廉，而且在以下几个方面有其独特的优越性。

34. You will get a 30% increase in production upon using this machine and also it allows one person to perform the tasks of three people.

一旦使用该机器，你们将会增产30%，而且一个人可以顶3个人使用。

35. This product will pay its own way in a year.

该产品一年就可收回成本。

36. This machine will pay back your investment in six months.

该机器半年就可收回投资。

37. The new type of suitcase car designed by our engineers is very ingenious and practical.

我方工程师设计的新款行李车非常精巧、实用。

38. This kind of bicycle can be folded in half and handy to carry around, especially useful during traveling and traffic jams.

这种自行车可以折迭，携带方便，在旅行中或交通堵塞时特别有用。

39. The maximum speed of this kind of variable-speed bicycle is 30 km per hour.

这种变速车每小时的最大速度是30km

40. These machines have few breakdowns and are easy to maintain because of their simple mechanical structure.

这些机器由于机械的构造简单，所以很少故障，易于保养。