F.2 Mathematics

2009-03-27 1:20 am
A postman delivered eight letters to four houses leaving at leaving at
least one at each house.
Which statement must be ture?
(A)Each house received more than one letter
(B)One house received at leat three letters.
(C)No house received more than two letter
(D)No house received more than five letters.
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回答 (1)

2009-03-27 1:30 am
✔ 最佳答案
Suppose there are 4 houses : House A,B,C and D
For answer (A):
the letters can be distributed as follows:
A:3 B:3 C:1 D:1
So , C and D have only one letter .
(A) is wrong.
For Answer (B):
the letters can be distributed as follows:
A:2 B:2 C:2 D:2
which shows that no houses received at leat three letters.
(B) is wrong.
For answer (C) ,
take the example in (A) as reference . A and B can have 3 letters .
(C) is wrong.
For answer (D) ,
If one of the houses (for example , A) has received more than five letters .i.e. A has six letters received.
A:6 B:1 C:1 D:0
which contradicts that at least one letter delievered at each house.
So, [No house received more than five letters] is true!


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