单选题
Questions refer to the following graph.
1977～1978 TEXTB()OK INVENTORY FOR SCHOOLS X AND Y BY YEAR OF PURCHASE (as a percent of the 1977～1978 inventory)
Note：All books were purchased new on July 1 of each year.
1977～1978 TEXTB()OK INVENTORY FOR SCHOOLS X AND Y BY YEAR OF PURCHASE (as a percent of the 1977～1978 inventory)
Note：All books were purchased new on July 1 of each year.
单选题
How many of the inventoried textbooks were purchased by the two schools combined during the years 1974, 1975, and 1976?
【正确答案】
D
【答案解析】[解析] 学校X在1974，1975，1976年购买的图书总数为：
1500×(13%+12%+8%)=495
学校Y在1974，1975，1976年购买的图书总数为：
2000×(18%+21%+8%)=940
两个学校购买图书的总数=495+940=1435
1500×(13%+12%+8%)=495
学校Y在1974，1975，1976年购买的图书总数为：
2000×(18%+21%+8%)=940
两个学校购买图书的总数=495+940=1435
单选题
If School X purchased 300 textbooks in 1971 and all of these textbooks either were counted in the inventory or had been discarded before the inventory, what percent of these textbooks had been discarded?
【正确答案】
C
【答案解析】[解析] 1971年学校X库存图书数目为：
1500×10%=150
所以被废弃图书所占的百分比为：
(300-150)÷300=50%
1500×10%=150
所以被废弃图书所占的百分比为：
(300-150)÷300=50%