※ 引述《Jinai (橘子汽水好喝~)》之铭言： : 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,我要用两条件才能解出来 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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