2016年1月19日SAT官方每日一題

　　2016年1月19日SAT官方逐日一題

　　標題範例：Mathematics > Standard Multiple Choice

　　Read the following SAT test question and then click on a button to select your answer.

　　If S is the set of positive integers that are multiples of 7, and if T is the set of positive integers that are multiples of 13, how many integers are in the intersection of S and T?

　　(A) None

　　(B) One

　　(C) Seven

　　(D) Thirteen

　　(E) More than thirteen

　　謎底：E

　　【剖析】The intersection of sets S and T is the set of integers that are in S and also in T. Set S consists of all positive integers that are multiples of 7, and set T consists of all positive integers that are multiples of 13, so the intersection of S and T is the set of positive integers that are multiples of both 7 and 13. This is the set of all positive integers that are multiples of 7*13=91. There are an infinite number of positive integers that are multiples of 91, so there are more than thirteen integers in the intersection of S and T.