仓库里有15吨钢材,第一小时用了总数的20%,第二小时用去4吨,还剩下多少吨钢材?
15-15×20%-4,
=15-3-4,
=8(吨),
答:还剩下8吨钢材.
If the population of the Earth goes on increasing at its present rate, by the middle of the 21stcentury we______all the oil that drives our cars.
A.will use up
B.will have used up
C.have used up
D.will have been using up
我国各地调查发现,有多少盲和视力损害是可以预防和可以治疗的()
A.1/3以上
B.1/2以上
C.1/4以上
D.1/5以上
E.所有盲和视力损害