下面是两道
1、Ifis the set of positive integers that are multiples of, and ifis the set of positive integers that are multiples of, how many integers are in the intersection ofand?
Answer Choices
(A) None
(B) One
(C) Seven
(D) Thirteen
(E) More than thirteen
The correct answer is E
Explanation
The intersection of sets and is the set of integers that are in and also in . Set consists of all positive integers that are multiples of , and set consists of all positive integers that are multiples of , so the intersection of and is the set of positive integers that are multiples of both and . This is the set of all positive integers that are multiples of . There are an infinite number of positive integers that are multiples of , so there are more than thirteen integers in the intersection of and .
2、If is divisible by , , and , which of the following is also divisible by these numbers?
Answer Choices
(A)
(B)
(C)
(D)
(E)
The correct answer is D
Explanation
Since is divisible by , , and , must be a multiple of , as is the least common multiple of , , and . Some multiples of are , , , , and .
If you add two multiples of , the sum will also be a multiple of . For example, and are multiples of and their sum, , is also a multiple of .
If you add a multiple of to a number that is not a multiple of , the sum will not be a multiple of . For example, is a multiple of and is not. Their sum, , is not a multiple of .
The question asks which answer choice is divisible by , , and ; that is, which answer choice is a multiple of . All the answer choices are in the form of "plus a number." Only choice (D), , has added to a multiple of . The sum of and is also a multiple of , so the correct answer is choice (D).
以上就是这两道SAT数学练习题的全部内容，后面的答案解析非常清晰详细。大家在备考SAT数学考试的时候，一定要以掌握解题的思路为备考的重点，对于知识点的补充要更加的全面，这样才能更好的迎接SAT数学考试。