推 Jinai:感謝~~ 01/02 03:33
※ 引述《Jinai (橘子汽水好喝~)》之銘言：
: 192. 18939-!-item-!-187;#058&011984
: Of the 75 houses in a certain community, 48 have a patio. How many of the
: houses in the community have a swimming pool?
: (1) 38 of the houses in the community have a patio but do not have
: a swimming pool.
: (2) The number of houses in the community that have a patio and
: a swimming pool is equal to the number of houses in the community that
: have neither a swimming pool nor a patio.
: ans:(B)
: 要如何解,我要用兩條件才能解出來
Suppose the number of houses with a swimming pool is 'X',
with both is 'b',
with neither is 'n'.
According to (2), we know b = n.
Therefore,
75 = 48 + X - b + n
75 = 48 + X
X = 27
The answer can be directly obtained just from (2)
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※ 編輯: micron 來自: 123.195.155.25 (01/01 21:03)