题干

实验中学为了了解该校学生课外阅读情况,随机抽查了50名学生,统计他们平均每周课外阅读时间t(h).枨据时间t的长短分为A,B,C,D四类.下面是根据所抽杳的人数绘制了不完整的统计表.其中a、b、c和d是满足a<b<c<d的正整数,请解答下面的问题:

50名学生平均每天课外阅读时间统计表

类别

A

B

C

D

时间t(h)

t<1

1≤t<2

2≤t<3

t≥3

人数

5a

5b

5c

5d

(1)写出表格中a+b+c+d的值.并求表格中的a、b、c、d的值;

(2)如果每分钟阅读200个字,每天坚持课外阅读时间为0.5h,一年(365天)能阅读多少本(10万字/本)书籍?

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答案(点此获取答案解析)

解:(1)5a+5b+5c+5d=50,a+b+c+d=10,

∵a<b<c<d,

∴a≥1,b≥2,c≥3,d≥4,

∴a+b+c+d≥10,

∴a=1,b=2,c=3,d=4;

(2)0.5×60×200×365÷100000=21.9≈22(或21)(本).

同类题3

阅读下列短文,从短文后各题所给的四个选项(A, B, C和D)中,选出可以填入空白处的最佳选项。

    I went with some colleagues from my office for a dinner in a very popular local restaurant. It was 1 business time and the restaurant was packed. We 2 found a table in a corner for three of us.

    As soon as we sat down, we heard a crash when a cleaning boy 3 the floor with all the plates he was carrying. There was 4 and no one was saying or doing anything.

    In a flash I remembered my 5 many years ago. Once, I 6 in the airport because I had rushed there on my own on an empty stomach. I was picked up and taken care of by two 7. Now this was my chance to 8 it forward.

    I ran to the young man's side immediately, turned him on his back and screamed for someone to 9 a hot drink. Soon people started asking if I was a doctor. I said I was not, 10 I was skillful at blacking out(晕厥).

    The kid soon opened his eyes, 11 what had happened. I 12 him by saying it was OK and I had had a 13 experience. He had not eaten anything. I held the 14 drink to his mouth till he finished it and sat with him till he felt OK.By then the 15 had arrived. I asked her to give the kid something to eat. I offered to pay.

    The manager was kind enough to refuse the 16 and agreed to make sure the kid ate before he went home. By the time all this was 17 it was getting late for my colleagues. We hadn't 18 anything yet, so they decided to go home.

    I slowly walked home, not hungry any more, feeling 19 for the opportunity I pay forward the 20 I had received many years ago.