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

    該機(jī)器半年就可收回投資。

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

    我方工程師設(shè)計(jì)的新款行李車非常精巧、實(shí)用。

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

    這種自行車可以折迭，攜帶方便，在旅行中或交通堵塞時(shí)特別有用。

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

    這種變速車每小時(shí)的最大速度是30km

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

    這些機(jī)器由于機(jī)械的構(gòu)造簡單，所以很少故障，易于保養(yǎng)。