A. 这个工厂生产的彩电已由 1986 年的 5000 台增加到 1990 年的21000 台。

The number of colour TV sets produced by the factory increased (rose , grew , climbed)　from 5000 in 1986 to 21000 in 1990.

B.参加者的人数增加到 30 万。The number of paticipants grew up to 300000 persons = increased , reaching 300000 persons).

C. 这个学校的教职工人数已减少到 700 人。The number of teaching staff members in this school has decreased to 700 persons.

5.(be)three times as + 形容词 + as 总产量 total output 钢的年产量 the annual output of 上升 17% rise by 17per cent steel 日产量 the daily output 导致产量下降 result in a diminished output

现在我们地区的粮食产量相当于 1970 年的 3倍。

The grain production (= output)in our area now is three times as great as that of 1970.

6.Compared with … , …

与去年相比，今年 13 项主要产品的产量都有大幅度增长。The factory has an output of 9 million cigarettes daily.

Compared with that of last year,the output of 13 main products (= items) this year has increased to a great extent.

7.There is (was) a rapid rise in … be on the rise

has been sharp increase on the increase

sudden decrease on the decline

steady decline

gradual fall

slow drop

slight

最近几年来这个地区的棉花产量有了迅速增长。